[CICD] Trigger benchmarks after a specific label was set

[sea212]

Currently the benchmark workflow is triggered, after changes were pushed to a specific staging branch. It is desired to trigger the benchmark workflow after a label like "s:benchmark-required" was set. The label should be replaced by another label once the bot is done, for example "s:benchmark-done" or the existing "s:in-progress" or even "s:review-needed".
In addition, manually triggering the workflow and therefore the benchmark process, could be useful in certain scenarios, e.g. when a benchmark is required before a release (which should not happen if everybody follows the process appropriately).

[sea212]

@lsaether Any preferences about the label names and what label the workflow should set after its done?
I think "s:benchmark-required" -> "s:benchmark-done" is fine for the default case.
There is another case though: When a new commit occurs during the benchmarks, the bot will stop the benchmark and not commit the changes. Make a state transition like "s:benchmark-required" -> "s:benchmark-aborted" would be useful in this scenario.