bazel_8: Add crucial packages to the standard shell environment

A lot of parts of bazel and standard packages ssume bash existence;
they should be able to call `/usr/bin/env bash`.

Also, `rules_python` uses python3 as a bootstrap way to call
other scripts (even if it uses its own interpreter).

Both of these are important and have been in the
bazel 7 package
  https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ba/bazel_7/package.nix#L87-L104
... but got lost in the bazel_8 package.

Things that used to compile with bazel 7 now break with bazel 8 on nix.

So: re-adding these crucial packages to the shell environment
bazel has available when executing actions.