Move the indexing back into DatabaseIndexingManager

For the sake of incremental updates, we moved all of the
conversion from PreIndexData to IndexData, and the
insertion of the rows into the SQLite DB into a new class,
IndexDataConverter. However, it's real role is just to
convert PreIndexData into IndexData.

So this CL moves the insertion of the rows back into
DatabaseIndexingManager.

Again, for the sake of simplicity, I did not change the
conversion flow. Rather, instead of inserting a row at the
end of the conversion, I just put it into a list which is
then returned. This lets me move the tests to appropriate
locations, without having to change them too much.

In the tests, the references to real xml layouts are
changed to fake references. Hooray for being less brittle.
IndexDataConverter now just tests that the IndexData
has the appropriate data from PreIndexdData.

Independently, we test that IndexData gets inserted in
DatabaseIndexingManager.

In the next CL, I'll refactor the conversion
flow for readability.

Bug: 33577327
Test: make RunSettingsRoboTests
Test: Took a database dump before and after change,
      and they were the same. Cool.

Change-Id: I39cc812d1f736e13a0a51af50984c239961ecf7a