Remove apply_mut and inspect_mut in favor of apply and inspect

[sunsided]

This simply makes FnMut closures the default.

[codecov[bot]]

Codecov Report

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

Project coverage is 95.15%. Comparing base (cfadfdd) to head (9d5e4dc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #26 +/- ## ========================================== - Coverage 95.16% 95.15% -0.02% ========================================== Files 31 31 Lines 5086 5074 -12 ========================================== - Hits 4840 4828 -12 Misses 246 246 ```

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