Consolidate addCountAnd{Pass|Drop}IfBytesAtR0Equal() to base class

Moved the addCountAndPassIfBytesAtR0Equal() and
addCountAndDropIfBytesAtR0Equal() methods to ApfV4GeneratorBase to
eliminate code duplication. Since APFv4 does not support
addJumpIfBytesatR0Equals(), both APFv4 and APFv6 implementations of
these methods are now identical.

Bug: 348529358
Test: TH
Change-Id: I2b9190d812ce0ebe3b5c13ca0d97322e227b40d8
3 files changed