Simplify IndexData builder

This is a small refactor in the large game of refactoring
DatabeseIndexingManager, and the general indexing pipeline
for Settings search.

This change is centered around hiding the normalization of
data (title, summary, keywords) from the data collector,
and putting that responsibility into the IndexData object.

In a future CL, we may move this again to the controller
that actually indexes the data.

Note, the conversion from PreIndexData to IndexData is
still messy, but until I can write a CL that just
rearranges the code, we must stay patient and vigilant.

Bug: 33577327
Test: make RunSettingsRoboTests
Change-Id: I53543d3d9c74a61380601297c55b6e4fea13031a