python-build-standalone provider / adhoc_binaries are not REAPI friendly

[cburroughs]

python-build-standalone provider / adhoc_binaries use a named cache which is not friendly to remote execution. See discussion and breadcrumbs at: #21422 (comment)

Just for remote caching it would be nice if this could be handled by REAPI instead of making a tarball out of named_caches.

(I am unsure if the same applies to the pyenv provider, or if the whole "we are compiling things with all sorts of tools" makes things different.)