[Feature] Add option to remove worked time from issue

[delvh]

• Gitea version (or commit ref): 1.13.1
• Git version: -
• Operating system: -

Description

As far as I am aware, it currently is impossible to remove time a collaborator has (not) spent working on an issue/ a PR.
This is not exactly appreciable as humans are error prone. The moment you enter a wrong time or the moment you stop (instead of cancel) a timer that was forgotten to be stopped i.e. yesterday, you have no way of undoing it, at least to my knowledge.
If you enter a negative number in the popup behind the Add time button, a RangeError gets thrown, which is totally fine.
But the option to manually remove worked time should at least somewhere be present for the average user.

What should be implemented

When the timer has not been activated, a (most-likely red) Remove time button should be displayed, at best to the right of the Add time button.

Tangentially related time tracking problem

If a user cancels a timer, the corresponding start and cancel event in the issue/ PR history should be removed.

[noerw]

duplicate of #2642 and will be fixed by #14100