Fix speech delay caused by audio ducking (#17806)
Fixes #17798, introduced by #17770.
Summary of the issue:
When audio ducking is enabled, the delay before each utterance increases significantly.
Description of user facing changes
The delay should return to a normal level compared to unaffected alpha versions.
Description of development approach
Instead of calling _setDuckingState to notify the system each time _ensureDucked is called, check the time passed since the last ducking to limit "redundant" calls to _setDuckingState to at most once per second. This prevents the delay caused by calling _setDuckingState too many times, but still allow audio ducking state to be reset when the next utterance starts more than one second later.
