Reindex db when package w/ searchIndexProvider changes

We do this by tracking a list of package/version that provides search
indexing data. When they change, we do a full reindex.

Change-Id: I85d4c4a994c7ff808662371c857cac1929a8b1cd
Merged-In: I906a1524f5b1292932f63727d605283ddb7d6ee2
Bug: 63903835
Test: robotests