Allow to run single Action remotely

[kolrami]

I have the use-case that I want to run a single action (in my case a py_test) via remote execution but all other actions in a sandbox locally. Unfortunately, I did not find a nice way of doing this. What I looked at:

• Put a special tag, but I only see tags to specify to disable remote execution. This is the other way round, I do not want to disable remote execution for a specific rule but I want to have it disabled overall but enable it for a single one.
• Set --spawn_strategy=sandboxed,local to disable remote exection overall and try to overwrite it using --strategy_regexp=... However, since I need this for a TestRunner mnemonic, this does not work (see --strategy_regexp does not seem to work for tests #18196).
• Instead of --strategy_regexp use --strategy=TestRunner=remote but that makes all tests remotely executed, I just want the single on being remotely executed. I see no way (in the py_test rule) to change the mnemonic to something else than TestRunner.

Do you have any idea how to achive what I need?