FormulaInstaller: cleanup check_/audit_ functions.
FormulaInstaller: move Cellar checks to module.
audit: use FormulaCellarChecks module.

Perform post-installation checks if a formula is installed.
Added for brew test-bot to be able to fail on bad Cellar installation.
brew-test-bot: audit after installation.

Enables new post-installation Cellar audit failures.

Closes #21242.