The first step of #23328

This PR cleans:

1. Dead function like `SubStr`
2. Unnecessary function like `UseHTTPS`, it should be provided by
`window.origin`
3. Duplicate function like `IsShowFullName`, there was already a
`DeafultShowFullName`

I have searched these removed functions globally, no use in code.

This PR is to fix the second problem mentioned in #23625, along with the
long texts problem in `issue-item-bottom-row` of `issuelist.tmpl`

Main changes are:
1. Add `max-width` to the search dropdowns in issue list and make the
possible long texts inside to show ellipsis if texts are long
2. Adjust the conditions in
[issuelist.tmpl](1d35fa0e78/templates/shared/issuelist.tmpl (L146-L167))
to fix the problem as mentioned by the
[comment](https://github.com/go-gitea/gitea/issues/23625#issuecomment-1479281060)
3. Use `word-break: break-word;` in `issue-item-bottom-row` to break the
possible long texts.

After the PR
issuelist in repo (similar for pr list):
<img width="366" alt="截屏2023-03-23 17 42 40"
src="https://user-images.githubusercontent.com/17645053/227163953-93e9adbd-5785-4c16-b538-9db901787775.png">

dropdowns with long name (Here take reference from github to deal with
the long names cases: show ellipsis with no title, because all these
options are clickable, and it might not be necessary to add titles to
them ):

<img width="370" alt="截屏2023-03-23 17 43 50"
src="https://user-images.githubusercontent.com/17645053/227164215-df6fcaaa-9fee-4256-a57c-053fbcffafbb.png">

<img width="365" alt="截屏2023-03-23 17 43 56"
src="https://user-images.githubusercontent.com/17645053/227164227-9c99abcd-f410-4e07-b5b8-cbce764eedcd.png">

issue page (similar for pr page):
<img width="374" alt="截屏2023-03-23 17 45 37"
src="https://user-images.githubusercontent.com/17645053/227164668-654a8188-dac8-4bbf-a6e3-f3768a644a1b.png">

on PC:
<img width="1412" alt="截屏2023-03-23 17 47 20"
src="https://user-images.githubusercontent.com/17645053/227166694-e7bcc6e5-9667-4cef-9fbf-db85640a2c6c.png">

<img width="1433" alt="截屏2023-03-23 17 46 40"
src="https://user-images.githubusercontent.com/17645053/227165182-4e2a5d19-74bc-4c66-b73c-23cbca176ffe.png">

This PR adds the ability to search both fullname and username for
assignees, reviewers and author search boxes when the config
[`DEFAULT_SHOW_FULL_NAME`](6ff5400af9/custom/conf/app.example.ini (L1238))
in `app.ini` is set to `true`. Which is originally raised
[here](https://projects.blender.org/infrastructure/blender-projects-platform/issues/14)
And if `DEFAULT_SHOW_FULL_NAME` is set to `false`(default value), these
search boxes will only show username.

Example:
When `DEFAULT_SHOW_FULL_NAME = true`

<img width="1220" alt="截屏2023-03-14 14 28 06"
src="https://user-images.githubusercontent.com/17645053/224914546-80ef2837-ab72-4d66-9f00-6eb77ed4baaa.png">

When `DEFAULT_SHOW_FULL_NAME = false` (default value)

<img width="1243" alt="截屏2023-03-14 14 29 37"
src="https://user-images.githubusercontent.com/17645053/224914798-f69ec8a2-0929-4330-827c-3e30188f9b47.png">


The specific search boxes that adapts these changes include:
1. Author, Assignee search boxes in pull requests tab and issues tab in
repository
<img width="1283" alt="截屏2023-03-14 14 35 01"
src="https://user-images.githubusercontent.com/17645053/224916250-8e452525-71d6-4b48-bf1c-bf7a176abaaa.png">

2. Assigee and Author on milestones issue page (Added missing search box
for author here)
<img width="1261" alt="截屏2023-03-14 14 38 20"
src="https://user-images.githubusercontent.com/17645053/224916569-d3105619-7824-4bb8-a6d0-1a600eaa9963.png">

3. Assignee on issues and PR Sidebar, Reviewer on PR Sidebar
<img width="976" alt="截屏2023-03-14 14 41 06"
src="https://user-images.githubusercontent.com/17645053/224917431-c45d821e-9660-4f58-a196-5979a0bb64ce.png">

<img width="1027" alt="截屏2023-03-14 14 41 58"
src="https://user-images.githubusercontent.com/17645053/224917290-ad4dbc52-0c20-45c4-9fce-9dcd59ad7d47.png">

4. Assignee when creating new issue
<img width="961" alt="截屏2023-03-14 14 44 33"
src="https://user-images.githubusercontent.com/17645053/224917694-34bee5a7-e975-4f37-8862-56ebc2556808.png">

5. Whitelisted users for pushing, Whitelisted users for merging and
Whitelisted reviewers in Protected branch settings
<img width="920" alt="截屏2023-03-14 14 48 56"
src="https://user-images.githubusercontent.com/17645053/224918551-9b46b44e-b075-4895-8d33-1aafc7d3c8e5.png">
<img width="901" alt="截屏2023-03-14 14 49 02"
src="https://user-images.githubusercontent.com/17645053/224918584-efa66f23-a593-4e26-a3eb-bb1fbc5516ae.png">
<img width="944" alt="截屏2023-03-14 14 49 21"
src="https://user-images.githubusercontent.com/17645053/224918591-be60455d-0513-4f66-84f6-b5e1bc40ff91.png">


6.  "Allowed users" in tags settings
<img width="935" alt="截屏2023-03-14 14 50 11"
src="https://user-images.githubusercontent.com/17645053/224918701-797699aa-c7e5-4290-b3fe-27dcead1c6c7.png">