Suppress "Long press power button to turn off TV" toast

The toast can be distracting and annoying when the user presses the
power button multiple times in a row,

This CL suppresses the toast if it was shown in the previous
`turnOffTvToastSuppressionDelay` milliseconds.

Bug: 427116348
Test: manual on device
Flag: NONE small change for TV only

Change-Id: Ib0aa65d19231edf81a08f3ad8a9fc55bffc3623d