Trim coordinate_transform.py, new features for spin method

[daico007]

PR Summary:

Remove the removed methods from coordinate_transform.py. Add anchor option for Compound.spin(), so now the compound can choose an anchor to be any of its successors instead of just its center.

Pending unit tests.

PR Checklist

---

• [ ] Includes appropriate unit test(s)
• [ ] Appropriate docstring(s) are added/updated
• [ ] Code is (approximately) PEP8 compliant
• [ ] Issue(s) raised/addressed?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.56%. Comparing base (ba6fead) to head (9bf4c3b). Report is 145 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1054 +/- ## ========================================== + Coverage 90.53% 90.56% +0.02% ========================================== Files 60 60 Lines 8423 8406 -17 ========================================== - Hits 7626 7613 -13 + Misses 797 793 -4 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.