chore: add validations to RootInstaller

[laur89]

• add extra sanity check to mount script - bail if package is still mounted after unmount execution
• RootInstaller:
  • install():
    • ensure mount script installation exits w/ 0;
    • ensure mount script execution exits w/ 0;
  • uninstall():
    • bail if package-to-be-unmounted is not mounted; indicates likely error on user part
    • ensure unmount script exits w/ 0;
• related to https://github.com/ReVanced/revanced-cli/issues/362

[laur89]

Sounds like a dud, closing.

[oSumAtrIX]

Some changes looked fine, may be worth it to keep the PR open with those changes