This adds a useful hook to be used for projects that use stestr,
it is primiative at the moment but covers most scenarios for using
it.

This PR also changes a Python module to start using it, once it
lands, follow up PRs can update all of them to use it tree-wide.

Signed-off-by: Vinetos <contact+git@vinetos.fr>

Prior to this change all python packages using `setuptools-rust` were broken when cross compiled as they built binaries for the build platform instead of for the host platform.

The setuptoolsRustBuildHook hook would have to be included as a native build input instead of the `setuptools-rust` package, but practically wasn't used anywhere.

This change makes it so that `setuptoolsRustBuildHook` becomes unnecessary, and instead `setuptools-rust` propagates a setup-hook directly setting up the build environment, similar to how cmake does it when included via nativeBuildInputs.

This change fixes cross on all packages using `setuptools-rust` as a build-system.

Closes: https://github.com/NixOS/nixpkgs/pull/449340
Fixes: https://github.com/NixOS/nixpkgs/issues/449325

This had already been removed and should be an alias now.

If sphinxHook runs before the fixup phase, possibly generated manpages
will get compressed in the fixup phase.

Fix the unterminated here document of the pytest-check-hook.sh
error mesage by moving the EOF of the here document
between the parenthesis of the process substitution.