Unified Storage/Search: Add max count config for indexing (#107255)

* Add max count config for indexing
* Build empty index when max count is exceeded
* Address linting
* Refactor buildIndexes
* Add test for max count threshold
* Update test doc comments
* Refactor TestBuildIndexes_MaxCountThreshold to not use mock framework
* Rename mocks used in TestBuildIndexes_MaxCountThreshold

* Refactor mockResourceIndex

* Test setting of indexing threshold configs

* Tweak comments, log

* Fix logging in buildEmptyIndex

* Export and reuse TestDocumentBuilderSupplier

* Reuse MockResourceIndex

pkg/storage/unified/resource/server.go

@@ -156,6 +156,10 @@ type SearchOptions struct {
 	// Skip building index on startup for small indexes
 	InitMinCount int
 
+	// Build empty index on startup for large indexes so that
+	// we don't re-attempt to build the index later.
+	InitMaxCount int
+
 	// Channel to watch for index events (for testing)
 	IndexEventsChan chan *IndexEvent