Cherrypick bug fixes from Icing
Descriptions:
========================================================================
Refactor DocHitInfoIteratorFilter
========================================================================
Remove polymorphism expansion from Icing
========================================================================
Fix the embedding index optimize bug found by monkey test
========================================================================
Fix document store
========================================================================
Only build and initialize embedding index data files when the index is non-empty
========================================================================
Bug: 337918394
Test: Presubmit
Change-Id: I34fa6ec75fd1aba6db11d242500207f78b756d80
13 files changed