just some refactoring bits towards replacing **util.OptionalBool** with
**optional.Option[bool]**

Since `modules/context` has to depend on `models` and many other
packages, it should be moved from `modules/context` to
`services/context` according to design principles. There is no logic
code change on this PR, only move packages.

- Move `code.gitea.io/gitea/modules/context` to
`code.gitea.io/gitea/services/context`
- Move `code.gitea.io/gitea/modules/contexttest` to
`code.gitea.io/gitea/services/contexttest` because of depending on
context
- Move `code.gitea.io/gitea/modules/upload` to
`code.gitea.io/gitea/services/context/upload` because of depending on
context

- Fix #29391

With this change, htmx will not follow the redirect in the AJAX request
but instead redirect the whole browser.

To reproduce the bug fixed by this change without waiting a long time
for the token to expire, you can logout in another tab then look in the
original tab. Just make sure to comment out both instances of
`window.location.href = appSubUrl` in the codebase so you won't be
redirected immediately on logout. This is what I did in the following
gifs.

Signed-off-by: Yarden Shoham <git@yardenshoham.com>
Co-authored-by: Giteabot <teabot@gitea.io>

Clarify when "string" should be used (and be escaped), and when
"template.HTML" should be used (no need to escape)

And help PRs like  #29059 , to render the error messages correctly.

Fix #26389

And complete an old TODO: `ctx.Params does un-escaping,..., which is
incorrect.`

The JSONRedirect/JSONOK/JSONError functions were put into "Base" context
incorrectly, it would cause abuse.

Actually, they are for "web context" only, so, move them to the correct
place.

And by the way, use them to simplify old code: +75 -196

Result of running `perl -p -i -e 's#interface\{\}#any#g' **/*` and `make fmt`.

Basically the same [as golang did](2580d0e08d).

1. Add "batch delete" button for selected issues, close #22273
2. Address the review in
https://github.com/go-gitea/gitea/pull/25219#discussion_r1229266083

1. The "web" package shouldn't depends on "modules/context" package,
instead, let each "web context" register themselves to the "web"
package.
2. The old Init/Free doesn't make sense, so simplify it
* The ctx in "Init(ctx)" is never used, and shouldn't be used that way
* The "Free" is never called and shouldn't be called because the SSPI
instance is shared

---------

Co-authored-by: Giteabot <teabot@gitea.io>

Follow #23290

Network error won't make content lost. And this is a much better
approach than "loading-button".

The UI is not perfect and there are still some TODOs, they can be done
in following PRs, not a must in this PR's scope.

<details>


![image](https://github.com/go-gitea/gitea/assets/2114189/c94ba958-aa46-4747-8ddf-6584deeed25c)

</details>

Co-author: @wxiaoguang 

Close #25096 

The way to fix it in this PR is to change form submit to fetch using
formData, and add flags to avoid post repeatedly.
Should be able to apply to more forms that have the same issue after
this PR.

In the demo below, 'approve' is clicked several times, and then
'comment' is clicked several time after 'request changes' clicked.

After:


https://github.com/go-gitea/gitea/assets/17645053/beabeb1d-fe66-4b76-b048-4f022b4e83a0


Update: screenshots from /devtest

>
![image](https://user-images.githubusercontent.com/2114189/245680011-ee4231e0-a53d-4c2a-a9c2-71ccd98005cc.png)
> 
>
![image](https://user-images.githubusercontent.com/2114189/245680057-9215d348-63d8-406d-8828-17e171163aaa.png)
> 
>
![image](https://user-images.githubusercontent.com/2114189/245680148-89d7b3d1-d7b6-442f-b69e-eadaee112482.png)

---------

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

Replace #16455

Close #21803

Mixing different Gitea contexts together causes some problems:

1. Unable to respond proper content when error occurs, eg: Web should
respond HTML while API should respond JSON
2. Unclear dependency, eg: it's unclear when Context is used in
APIContext, which fields should be initialized, which methods are
necessary.


To make things clear, this PR introduces a Base context, it only
provides basic Req/Resp/Data features.

This PR mainly moves code. There are still many legacy problems and
TODOs in code, leave unrelated changes to future PRs.