Respect "skip unittest" user configuration #451

Job	Run time
Run all tests (dmd-latest, dmd, ubuntu-22.04, make)	3m 0s
Run all tests (dmd-latest, dmd, ubuntu-22.04, dub, current)	1m 33s
Run all tests (dmd-latest, dmd, ubuntu-22.04, dub, min libdparse)	1m 40s
Run all tests (dmd-latest, dmd, windows-latest, make)	1m 40s
Run all tests (dmd-latest, dmd, windows-latest, dub, current)	2m 19s
Run all tests (dmd-latest, dmd, windows-latest, dub, min libdparse)	2m 45s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, make)	2m 46s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, dub, current)	1m 8s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, dub, min libdparse)	1m 22s
Run all tests (ldc-latest, ldmd2, macos-latest, make)	2m 46s
Run all tests (ldc-latest, ldmd2, macos-latest, dub, current)	1m 43s
Run all tests (ldc-latest, ldmd2, macos-latest, dub, min libdparse)	2m 7s
Run all tests (ldc-latest, ldmd2, windows-latest, make)	5m 49s
Run all tests (ldc-latest, ldmd2, windows-latest, dub, current)	3m 3s
Run all tests (ldc-latest, ldmd2, windows-latest, dub, min libdparse)	3m 24s
Run all tests (dmd-latest, gdc-12, ubuntu-22.04, make)	7m 22s
Run all tests (dmd, macos-13, dub, current)	1m 44s
	46m 11s

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