Part of #27065

This reduces the usage of `db.DefaultContext`. I think I've got enough
files for the first PR. When this is merged, I will continue working on
this.

Considering how many files this PR affect, I hope it won't take to long
to merge, so I don't end up in the merge conflict hell.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

Before, Gitea shows the database table stats on the `admin dashboard`
page.

It has some problems:

* `count(*)` is quite heavy. If tables have many records, this blocks
loading the admin page blocks for a long time
* Some users had even reported issues that they can't visit their admin
page because this page causes blocking or `50x error (reverse proxy
timeout)`
* The `actions` stat is not useful. The table is simply too large. Does
it really matter if it contains 1,000,000 rows or 9,999,999 rows?
* The translation `admin.dashboard.statistic_info` is difficult to
maintain.

So, this PR uses a separate page to show the stats and removes the
`actions` stat.


![image](https://github.com/go-gitea/gitea/assets/2114189/babf7c61-b93b-4a62-bfaa-22983636427e)

## :warning: BREAKING

The `actions` Prometheus metrics collector has been removed for the
reasons mentioned beforehand.
Please do not rely on its output anymore.

Change all license headers to comply with REUSE specification.

Fix #16132

Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>

* Move some files into models' sub packages

* Move functions

* merge main branch

* Fix check

* fix check

* Fix some tests

* Fix lint

* Fix lint

* Revert lint changes

* Fix error comments

* Fix lint

Co-authored-by: 6543 <6543@obermui.de>

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

* Move access and repo permission to models/perm/access

* fix test

* fix git test

* Move functions sequence

* Some improvements per @KN4CK3R and @delvh

* Move issues related code to models/issues

* Move some issues related sub package

* Merge

* Fix test

* Fix test

* Fix test

* Fix test

* Rename some files

* Move almost all functions' parameter db.Engine to context.Context
* remove some unnecessary wrap functions

* Move access and repo permission to models/perm/access

* Remove unnecessary code

Add statistic information for total user count, active user count, issue count and comment count for `/nodeinfo`

* Move milestone to models/issues/

* Fix lint

* Fix test

* Fix lint

* Fix lint

* Move project files into models/project sub package

* Fix test

* Fix test

* Fix test

* Fix build

* Fix test

* Fix template bug

* Fix bug

* Fix lint

* Fix test

* Fix import

* Improve codes

Co-authored-by: 6543 <6543@obermui.de>

* Move organization related structs into sub package

* Fix test

* Fix lint

* Move more functions into sub packages

* Fix bug

* Fix test

* Update models/organization/team_repo.go

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

* Apply suggestions from code review

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

* Fix fmt

* Follow suggestion from @Gusted

* Fix test

* Fix test

* Fix bug

* Use ctx but db.DefaultContext on routers

* Fix bug

* Fix bug

* fix bug

* Update models/organization/team_user.go

* Fix bug

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

* some repository refactors

* remove unnecessary code

* Fix test

* Remove unnecessary banner

* Move keys to models/keys

* Rename models/keys -> models/asymkey

* change the missed package name

* Fix package alias

* Fix test

* Fix docs

* Fix test

* Fix test

* merge

* Some refactors related repository model

* Move more methods out of repository

* Move repository into models/repo

* Fix test

* Fix test

* some improvements

* Remove unnecessary function

* Move user related model into models/user

* Fix lint for windows

* Fix windows lint

* Fix windows lint

* Move some tests in models

* Merge

* Move attachment into models/repo/

* Fix test

* Fix bug

* Move UserRedirect into models/user/

* Fix lint & test

* Fix lint

* Fix lint

* remove nolint comment

* Fix lint

* Move user follow and openid into models/user

* Ignore the lint

* Ignore the lint

* Fix test

* ignore stutters lint on UserOpenID

* Add metrics to get issues by label

* Add comment on IssueByLabelCount

* Code review - Unify "AS" in SQL (#17201)

* Code review - Remove useless join (#17201)

* Code review - Disable issue_by_label by default in settings (#17201)

* use e

* restore empty line

* update docs

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <matti@mdranta.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* Add projects and project boards in exposed metrics

* Refactor db.GetEngine

Co-authored-by: delvh <dev.lh@web.de>

* Move login related structs and functions to models/login

* Fix test

* Fix lint

* Fix lint

* Fix lint of windows

* Fix lint

* Fix test

* Fix test

* Only load necessary fixtures when preparing unit tests envs

* Fix lint

* Fix test

* Fix test

* Fix error log

* Fix error log

* Fix error log

* remove unnecessary change

* fix error log

* merge main branch

* DBContext is just a Context

This PR removes some of the specialness from the DBContext and makes it context
This allows us to simplify the GetEngine code to wrap around any context in future
and means that we can change our loadRepo(e Engine) functions to simply take contexts.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix unit tests

Signed-off-by: Andrew Thornton <art27@cantab.net>

* another place that needs to set the initial context

Signed-off-by: Andrew Thornton <art27@cantab.net>

* avoid race

Signed-off-by: Andrew Thornton <art27@cantab.net>

* change attachment error

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Move db related basic functions to models/db

* Fix lint

* Fix lint

* Fix test

* Fix lint

* Fix lint

* revert unnecessary change

* Fix test

* Fix wrong replace string

* Use *Context

* Correct committer spelling and fix wrong replaced words

Co-authored-by: zeripath <art27@cantab.net>