Code cleanup pass on all of NPVC

* Delete dead code
* Delete unnecessary code (e.g. 1 line methods called only once)
* Reduce API surface by reducing visibility wherever possible
* Remove unnecessary params that are always the same value
* Remove unnecessary returns that are always the same value
* Eliminate redundancies (e.g. multiple forms of debug logging)
* Make all member vars private
* Add bug ticket IDs to TODOs
* Shrink short 3 line comments to one line
* Convert single method inner classes to lambdas
* Consistent method naming (e.g. getFoo, isFoo, startFoo, onFoo)
* Move member vars declared in the middle of the class
* Move runnable declarations to the end of the init block
* Extract large methods declared inside other methods
* Make javadoc style more consistent
* Add 'final' wherever possible

I've done my best to reduce the negative impact on git blame,
and I think what remains is acceptable given the amount of churn
we expect this class to undergo in the coming months.

Bug: 237661616
Test: atest and manual
Change-Id: Ie0135b8b0d7dbc0263c616c9405001e3730336b7