chore(ci): migrate Linux CI to runs-on self-hosted runners #5975

Job	Run time
check-xarray-docs	13s
build-wheels	3m 6s
build-wheels-free-threaded	3m 1s
test-free-threaded	2m 9s
stubtest	17s
test (latest, latest-release, latest-release, latest-release, latest-release)	1m 46s
test-hypothesis-shard (2)	3m 18s
xarray-backends (minimum, 2025.07.1, 3.1.0)	1m 27s
test (minimum, 2025.07.1, 2025.2.0, 2025.2.0, 3.1.0)	1m 49s
compat-stateful	2m 24s
test-hypothesis-shard (0)	48s
xarray-backends (latest-release, latest-release, latest-release)	1m 27s
test-hypothesis-shard (1)	4m 40s
test-hypothesis	5s
	26m 30s

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