python@3.7: update resources, link into HOMEBREW_PREFIX

[carlocab]

• python@3.7: update resources
• python@3.7: use altinstall target
• python@3.7: cleanup
• versioned_keg_only_allowlist: add python@3.7
• python@3.7: fix missing symlinks

This backports the changes from #107517 so that python@3.7 can be linked into HOMEBREW_PREFIX.

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[BrewTestBot]

@carlocab has triggered a merge.