Camera: Ensure device events are processed in order

Camera devices will use a client provided executor
to handle all internal events. Typically executors
provided by clients are limited and running in a single
thread which makes it safe for the current implementation
to make assumptions about the ordering.
In some cases like the Kotlin 'Dispatchers.IO', the device
executor can utilize a pool of threads. The ordering
of events in this case could be random and depend on timing
and scheduling decisions resulting in different kinds of
errors and unexpected states.
To avoid this, ensure that the critical device state
handling is done by a single thread executor and is always
in the order expected by the implementation.

Bug: 305857746
Test: Manual using camera application
Change-Id: I33eed3db275be92422db2a646fcfc68d5a64f880