Factor out BoostRoot and check-quick jobs into triggerable workflow

[Flamefire]

This allows manually running the workflow e.g. to test recent changes in the main Boost project/libraries.

The idea is that library authors can request to run these 2 jobs after merging to develop/master to check it works in general and across different CMake versions

[pdimov]

How would library authors request that?

[Flamefire]

Via Slack or ML. I figured here is the best way to test things CMake.

Putting it into boostorg/boost instead to run on every submodule update commit might be too much, but possibly better as more complete/immediate. What do you think?

[pdimov]

I split the workflows in a slightly different way.

[Flamefire]

So this

4 times the jobs to 457, MS will love us ;-)

What's missing is the workflow trigger for the cmake_versions.yml

I really think it makes sense to be able to trigger running just that without making a commit here e.g. when checking a change from a library for whether it works for all CMake versions or when it does fail. Or before releases. At least the tags should trigger a run so we notice it for RCs at least when they are tagged. With the trigger we can run it for the beta before that.

[pdimov]

RCs aren't tagged, but the betas are, so it probably makes sense to make CI run on tags.

You can add the workflow-dispatch in subsequent PRs if you like.