EGL Multifile Blobcache: Handle lost cache

During execution, if the app's cache is cleared from outside
our control, two issues occur:

* New entries won't persist to disk because the multifile directory
  is missing.
* applyLRU will abort eviction, allowing entries beyond the limits.

To address this, this CL:
* Adds missing directory detection to our deferred write thread
  which then attempts to recreate it and continue.
* Updates eviction to issue a warning rather than abort so it can
  update tracking and continue.

For missing entries, the app will get hits from hotcache, but
anything beyond that will become a miss.

Additional tests:
* RecoverFromLostCache
* EvictAfterLostCache

Based on work by: Igor Nazarov <i.nazarov@samsung.com>

Test: libEGL_test, EGL_test, ANGLE trace tests, apps
Bug: b/351867582, b/380483358
Flag: com.android.graphics.egl.flags.multifile_blobcache_advanced_usage
Change-Id: I13c8cdf58c957163eed4498c0d4be180574bf03e