[Merged by Bors] - Use dedicated PoST service for Proof generation #15073

Job	Run time
filter-changes	7s
lint	3m 18s
quicktests	2m 20s
build (ubuntu-latest)	1m 50s
unittests (ubuntu-latest)	11m 27s
build (self-hosted, linux, arm64)	20s
unittests-slower (self-hosted, linux, arm64)	12m 45s
unittests (macos-latest)	11m 22s
build (macos-latest)	1m 23s
unittests (self-hosted, macos, arm64)	11m 11s
unittests-slower (windows-latest)	12m 33s
build (self-hosted, macos, arm64)	55s
build (windows-latest)	6m 51s
ci-status	5s
	1h 16m 27s

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