Enable ProfileSaver to have a different delay for the first ever save

The runtime now supports -Xps-first-save-ms, which when configured
may alter the delay for the first ever profile save. Subsequent
saves will proceed based on the existing -Xps-min-save-period-ms.

The first ever save is an approximation, and computed by checking
the profiles size.

Test: gtest & manual
Bug: 185979271
Change-Id: I7119b9d2b8829653046565426090c89f6a619a27
6 files changed