EGL Multifile Blobcache: Add status file

Add a status file that contains the cache version and
platform build ID.  On future startups, if those values
don't match, clear the cache.

This alleviates a problem on driver updates, which cause
all new queries to miss, creating new entires, filling the
cache.  For apps with many small entries, the start up
time has become a problem.

Test: libEGL_test, EGL_test, ANGLE trace tests, apps
Bug: b/295051628
Bug: b/310535559
Change-Id: I17b91fb6c994237fb5c2a220db4f23050d45742b