fix: output wrong WppEntryOffset when emulating start code at end of WPP row
doc: improve documentation for --stats and multi-pass in general
ppa: minimize code foot-print of profiling events

This will allow us to add support for more profiling systems without littering
the code
ppa: simplify interfaces, enforce coding style
ppa: refine event names

Drop the unused names, remove uninteresting events.  Try to cover the main
thread pool tasks and the frame encoder times.
ppa: emit one event per CTU for more clarity, disable frame threads events

The frame threads are generally uninteresting when WPP is in use
asm: idct[8x8] sse2 12232 -> 3500 over c code  3550 -> 3500 over intrinsic
fix 4:4:4 rd<=1