[3.15] gh-151929: Add pythoninfo commands to Platforms/WASI (GH-152136) (#152222)

[3.15] gh-151929: Add pythoninfo commands to Platforms/WASI (GH-152136) (#152222)

gh-151929: Add pythoninfo commands to Platforms/WASI (GH-152136)

The "build" command now also runs "pythoninfo-build" and
"pythoninfo-host" commands.

If no subcommand is provided, display the help.

GitHub Action "WASI":

* Add "pythoninfo-build" and "pythoninfo-host" commands.
* Remove unused and outdated CROSS_BUILD_PYTHON environment variable.
(cherry picked from commit 7c8163719cd23d41daeaed0b243be45de3e82e05)

Co-authored-by: Victor Stinner <vstinner@python.org>