Eager Per Row Debouncing added (added to Ergodox) (#5498)

Eager Per Row Debouncing added (added to Ergodox) (#5498)

* Implemented Eager Per Row debouncing algorithm.

Good for when fingers can only press one row at a time (e.g. when keyboard is wired so that "rows" are vertical)

* Added documentation for eager_pr

* Ported ergodox_ez to eager_pr debouncing.

* Removed check for changes in matrix_scan.

* Added further clarification in docs.

* Accidental merge with ergodox_ez

* Small cleanup in eager_pr

* Forgot to debounce_init - this would probably cause seg-faults.