Add audit check to see if both version and checksum changed.

formula: ensure HOMEBREW_PREFIX/bin in test PATH.

formula: build dependencies are never missing.

Only likely to kick in when environment filtering is enabled.

Otherwise we need to tediously add a dramatic number of PATHs to tests
or recurse through the runtime formulae dependencies and add all them.

CC @ilovezfs

If the formula is already installed and they've been removed: that's ok.

Fixes #2625.

replace_text_in_files: Regex match is greedy

audit: fix full versioned alias name resolution in taps

Use scoped RSpec matchers.

Support GPG (signed data) container in Homebrew Cask

Fix implicit conversion of nil into string error