chore: More Bash improvements and removing deprecations

[hyperupcall]

• Improve quoting, especially in places where filepaths are used
• No longer use which, which is deprecated in Debian and has issues - use command -v instead
  • This ends up modifying brew-release.path to match (just to note)
• No longer use deprecated egrep
• No longer use deprecated [ -o or ``

[spacewander]

Have you tested if command -v works with a fresh Mac?

[hyperupcall]

The usage is specified in POSIX. And I have used it before, passing Mac CI on my other Bash apps

For your benefit I just tested it with Bash 3.2 on Catalina and it works flawlessly