- Currently in the cron tasks, the 'Previous Time' only displays the
previous time of when the cron library executes the function, but not
any of the manual executions of the task.
- Store the last run's time in memory in the Task struct and use that,
when that time is later than time that the cron library has executed this
task.
- This ensures that if an instance admin manually starts a task, there's
feedback that this task is/has been run, because the task might be run
that quick, that the status icon already has been changed to an
checkmark,
- Tasks that are executed at startup now reflect this as well, as the
time of the execution of that task on startup is now being shown as
'Previous Time'.
- Added integration tests for the API part, which is easier to test
because querying the HTML table of cron tasks is non-trivial.
- Resolves https://codeberg.org/forgejo/forgejo/issues/949

(cherry picked from commit fd34fdac1408ece6b7d9fe6a76501ed9a45d06fa)

Co-authored-by: KN4CK3R <[email protected]>