Camera: HeicCompositeStream: Fix IDLE state transition

It's not sufficient to check mPendingInputFrames for wether
the device is idle. mSettingsByFrameNumber contains requests
not yet queued into mPendingInputFrames. And it also needs to be
considered.

Flag: EXEMPT bugfix
Test: vendor test
Bug: 361290241
Change-Id: I9d9a71b2ed29f2191b824078b8fc54ac6250d890
(cherry picked from commit 40450570)