Cleaning up duplicate proto for ProcessStartTime

There is no need to maintain two copies of the same proto message.
Moving framework to directly use the canonical proto used by statsd.

Test: m -j statsd_testdrive
out/host/linux-x86/bin/statsd_testdrive 169

Bug: 242928495
Change-Id: Ie2bdd2151dae26a611c3905342bb49ddddf2788d
Merged-In: Ie2bdd2151dae26a611c3905342bb49ddddf2788d
(cherry picked from commit e6073bc3ce37f0a29018ee0e02a0376f4c37da62)
(cherry picked from commit 83327c47f549db792e43f12385847f2b9b0006e5)
Merged-In: Ie2bdd2151dae26a611c3905342bb49ddddf2788d
2 files changed