Uses macOS keychain for storage of AWS credentials

Current versions

Formula history

ilovezfs Audit fixes for descriptions (#20013)
Izzy Navedo Replace references to “(Mac) OS X” with “macOS”.
Mike McQuaid aws-keychain: bottle unneeded.
Mike McQuaid aws-keychain: cleanup test.
Elliot Murphy aws-keychain: assert on test output.
Elliot Murphy aws-keychain: use full path to executable in test.
Elliot Murphy aws-keychain: use shell_output instead of system
Elliot Murphy aws-keychain 3.0 (new formula)