[Proposal] Do not autoreload page after any action in the issue management

[delvh]

• Gitea version (or commit ref): 1.15.0+dev-152-gc29e85228 and below (1.14.1)
• Can you reproduce the bug at https://try.gitea.io:
  • Yes

Description

Currently, after almost any action for an issue (simply closing the label dropdown, adding/ clearing a project from/ to an issue, … ), the page gets reloaded, which proves quite time intensive when trying to manage issues and having to wait 1-2 seconds between each action.
I think it would be better if the changes would be posted silently without always reloading the page.
I also think that is a bug because I do not remember this kind of behavior before v1.14.0/1.14.1 (don't know which exactly).

[lunny]

We should switch reload the page to ajax.