Add Python Android support

[mhsmith]

I'm currently targeting the 3.0.0 branch as part of a project I'm working on, but I'll rebase this PR on main once it's complete.

• Requires Android improvements needed for building NumPy and related packages pypa/cibuildwheel#2695
• Requires BLD: Add Android support numpy/numpy#30412
• Requires BLD: Add Android support scipy/scipy#24341

[trivialfis]

Thank you for working on this. Please let us know if there's anything we can help.

[mhsmith]

The wheels here were built using the same procedure as numpy/numpy#30412 (comment).

I haven't attempted to run the full test suite on these wheels yet, but they pass the Chaquopy smoke tests with the help of this workaround.

[trivialfis]

I haven't attempted to run the full test suite on these wheels yet

The test should be good enough for now if you can compile XGBoost and run it. Not an android developer, I assume aarch64 android is quite similar to other aarch64 linux distributions.

related: #10656

[poti1]

Any updates on this branch? (please let us know if we can somehow help).

[mhsmith]

This PR is at the end of a chain of dependent PRs (see the top comment), each of which will need to be released before the next one can be merged. So it may be a few months before I can come back to it, but I won't forget about it.