Improve ProfileSaver to cache data and do minimal I/O

This CLs introducing caching to further optimize the I/O performed by
the ProfileSaver. The cache stats are also recorded.

Resolved classes are captured and cached after 2 seconds but written
later during application lifetime.

Methods are also cached and the write got smarter to avoid
reading/writing them if it's not needed.

On non scientific experiments the size of the cache reaches just a few
hundreds uint16_t values kept in set, so its impact is minimal.

In terms of how much data we write. In the same non scientific
experiments this reduces the total bytes written by at least 2-3x. In
the first few minutes of after the boot gmscore writes ~3KB (down from
9kb) and quicksearchlauncher writes ~20KB (down from 40KB).

Bug: 27600652

Change-Id: I3a4e7051ccf04ac8fbd5896d328692db773e979d