Add tests for tuple lifting and unfitting
Add test for unliftable not found scenario
Add separate test for using SubpatternsAttachment from a macro
Test possible quasiquote runtime failures
Address minor pull request feedback points

1. Use (x1, x2): (T1, T2) instead of (x1: T1, x2: T2)

2. More detailed error message for improper function argument

3. Fix typo

4. Completely remove LiftableClass symbol from definitions