Make the indexName functions more obviously laid out

Make the indexName functions more obviously laid out

Move Sqlites's indexName to Database to have no remapping by default.
This is because MSSQL and Postgresql both don't need remapping, it's
just MySQL that's the problem.

So move the one from Database into MysqlBase to only do the remappings
there.

Also fix up the comments to make them less vague, not mentioning tables
when the function has no table parameter passed, so hence, no context
as to which table said index is wanted to be used

Bug: T154872
Change-Id: I46c575771e6cb36176bcf6cd1a865b703db0275d