Runner restart should not create new runner id

### Feature Description

Whenever a runner is restarted, it creates a new entry in the `/-/admin/actions/runners` runners list which then accumulates many dead "runners" over time. It would be better to just update the existing runner instead.

Maybe each runner could remember the id it was created on, or Gitea could gain some other way to identify "same runner".

### Screenshots

_No response_