Port Azure CI jobs to new GitHub Actions workflow

[kinke]

[dlang-bot]

Thanks for your pull request and interest in making D better, @kinke! We are looking forward to reviewing it, and you should be hearing from a maintainer soon. Please verify that your PR follows this checklist:

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[ibuclaw]

@kinke who's going to be using this?

[kinke]

Oh, completely forgot about this PR. ;) - No idea, but I was porting LDC CI from Azure Pipelines to GH Actions at that time, so thought I could port this stuff here too while memory is fresh...

[Geod24]

Looks good! Can you rebase (and apply the diff from HEAD) so we can merge ?

[kinke]

Done.

[kinke]

Hmm, CI ran 2 months ago: https://github.com/dlang/installer/actions/workflows/build_windows.yml - not anymore apparently?

[ibuclaw]

Hmm, CI ran 2 months ago: https://github.com/dlang/installer/actions/workflows/build_windows.yml - not anymore apparently?

Not patient enough for the trigger to take effect. ;-)