Add Python 3.15 test infrastructure #2462

Job	Run time
stub_uploader tests	4m 58s
stubtest: third party (windows-latest, 2)	2m 13s
stubtest: third party (windows-latest, 0)	1m 31s
stubtest: third party (ubuntu-latest, 2)	6m 48s
stubtest: third party (windows-latest, 1)	1m 50s
stubtest: third party (ubuntu-latest, 3)	9m 45s
stubtest: third party (windows-latest, 3)	2m 4s
stubtest: third party (ubuntu-latest, 0)	7m 32s
stubtest: third party (macos-latest, 3)	1m 16s
stubtest: third party (macos-latest, 2)	40s
stubtest: third party (ubuntu-latest, 1)	6m 9s
stubtest: third party (macos-latest, 0)	48s
stubtest: stdlib (windows-latest, 3.11)	1m 18s
stubtest: stdlib (macos-latest, 3.15)	1m 11s
stubtest: stdlib (macos-latest, 3.10)	46s
stubtest: third party (macos-latest, 1)	1m 0s
stubtest: stdlib (ubuntu-latest, 3.14)	39s
stubtest: stdlib (windows-latest, 3.15)	1m 48s
stubtest: stdlib (windows-latest, 3.13)	1m 13s
stubtest: stdlib (windows-latest, 3.12)	1m 10s
stubtest: stdlib (ubuntu-latest, 3.15)	45s
stubtest: stdlib (ubuntu-latest, 3.12)	45s
stubtest: stdlib (ubuntu-latest, 3.10)	36s
stubtest: stdlib (macos-latest, 3.14)	32s
stubtest: stdlib (windows-latest, 3.14)	1m 19s
stubtest: stdlib (macos-latest, 3.11)	28s
stubtest: stdlib (macos-latest, 3.13)	30s
stubtest: stdlib (macos-latest, 3.12)	37s
stubtest: stdlib (ubuntu-latest, 3.13)	34s
stubtest: stdlib (ubuntu-latest, 3.11)	38s
Create issue on failure	0s
	1h 1m 23s

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