ci: Finish migration to Github Actions #29

Job	Run time
Soundness / API breakage check	2m 34s
Soundness / Documentation check	29s
Soundness / Unacceptable language check	0s
Soundness / License headers check	5s
Soundness / Broken symlinks check	3s
Soundness / Format check	33s
Checks / Cxx interop / 5.8	37s
Checks / Cxx interop / 5.9	1m 19s
Checks / Cxx interop / 5.10	1m 24s
Checks / Cxx interop / nightly-6.0	1m 41s
Checks / Cxx interop / nightly-main	1m 43s
Checks / Unit tests / 5.8	33s
Checks / Unit tests / 5.9	1m 30s
Checks / Unit tests / 5.10	1m 29s
Checks / Unit tests / nightly-6.0	2m 18s
Checks / Unit tests / nightly-main	1m 46s
	18m 4s

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