Add Python 3.15 test infrastructure #2463

Job	Run time
stub_uploader tests	1m 55s
stubtest: third party (windows-latest, 1)	1m 31s
stubtest: third party (macos-latest, 1)	1m 16s
stubtest: third party (ubuntu-latest, 2)	1m 56s
stubtest: third party (macos-latest, 3)	1m 21s
stubtest: third party (windows-latest, 3)	1m 29s
stubtest: third party (ubuntu-latest, 0)	1m 56s
stubtest: third party (macos-latest, 2)	46s
stubtest: third party (windows-latest, 0)	1m 26s
stubtest: third party (macos-latest, 0)	53s
stubtest: third party (ubuntu-latest, 3)	1m 57s
stubtest: stdlib (windows-latest, 3.15)	1m 24s
stubtest: stdlib (ubuntu-latest, 3.12)	30s
stubtest: stdlib (ubuntu-latest, 3.15)	50s
stubtest: stdlib (ubuntu-latest, 3.11)	40s
stubtest: stdlib (windows-latest, 3.14)	1m 29s
stubtest: third party (windows-latest, 2)	1m 56s
stubtest: stdlib (ubuntu-latest, 3.10)	50s
stubtest: stdlib (windows-latest, 3.13)	1m 49s
stubtest: stdlib (macos-latest, 3.15)	1m 2s
stubtest: stdlib (macos-latest, 3.10)	1m 8s
stubtest: stdlib (ubuntu-latest, 3.14)	42s
stubtest: stdlib (ubuntu-latest, 3.13)	38s
stubtest: stdlib (macos-latest, 3.11)	44s
stubtest: stdlib (macos-latest, 3.13)	30s
stubtest: third party (ubuntu-latest, 1)	1m 56s
stubtest: stdlib (macos-latest, 3.12)	33s
stubtest: stdlib (macos-latest, 3.14)	25s
stubtest: stdlib (windows-latest, 3.11)	1m 12s
stubtest: stdlib (windows-latest, 3.12)	1m 23s
Create issue on failure	1s
	36m 8s

Provide feedback