Use the same reason for OTAs and First Boots

Quicken is now deprecated and there is no good reason to have OTAs
handled differently then first boots when it comes to the compiler
filter.

With this changes we will have:
- OTA and FirstBoot using pm.dexopt.first-boot reason
- BackgroudDexOptService# post-boot job using pm.dexopt.boot reason

Also, clean dalvik-cache pruning which is no longer a thing.

Test: m
Bug: 172114559
Change-Id: I75b388b211314bcc7cfee8d8394c3d81ffef2cc7