Allow the use of arbitrary Pyodide versions #4584

Job	Run time
Linters (mypy, flake8, etc.)	1m 4s
Test on ubuntu-latest (3.13)	44m 26s
Test on windows-latest (3.13)	43m 20s
Get qemu emulated architectures	14s
Test cibuildwheel building Pyodide wheels (default version)	5m 52s
Test on macos-13 (3.13)	26m 42s
Test cibuildwheel building Pyodide wheels (custom version)	6m 1s
Test on macos-14 (3.13)	13m 18s
Test on ubuntu-latest (3.8)	46m 3s
Test Linux aarch64 using qemu	28m 8s
Test Linux armv7l using qemu	16m 35s
Test Linux ppc64le using qemu	17m 38s
Test Linux s390x using qemu	20m 26s
	4h 29m 47s

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