Should the positions of the cursor or selection be immediately snapped when snapping is turned on?

### Your idea

The behaviour in 3.3.0 and previous versions is the when snapping is turned on, the cursor or the selection are immediately snapped to some unit.
I think the user might expect this to happen only when they adjust their positions, rather than also immediately after snapping is turned on.
This is more of an issue in 3.3.0, where:
1. The user can't adjust the snap to unit before snapping is turned on.
2. With snapping on, if a user changes the snap to unit using up/down arrow, the cursor or selection are snapped to each unit as the unit is changed.

If it is decided that the positions of the cursor or selection should be snapped immediately after snapping is turned on, then it would be better if the snap to combo box was always available for adjustment.

### Problem to be solved

The cursor or selection being snapped to a unit which the user does not want.

### Prior art

_No response_

### Additional context

_No response_

No files or tests are identified in the issue. Reproduce the snapping behavior in Audacity 3.3.0 while toggling snapping and changing the snap-to unit with the arrow keys; clarify the expected behavior before implementation.

Written by the indexing model from the issue text.