EGL Multifile Blobcache: Remove entries when valueSize is zero

When set is called with a value size of zero, the cache will simply remove
the entry from disk and return.

Any pending writes will complete before the entry is removed.

Additional tests:
* ZeroSizeRemovesEntry

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

Test: libEGL_test, EGL_test, ANGLE trace tests, apps
Bug: b/355259618, b/380483358
Flag: com.android.graphics.egl.flags.multifile_blobcache_advanced_usage
Change-Id: I092a0e41c587ac036311b5e08e8b6ffa59588bca