[Fix #1340] Fix a false positive for Rails/WhereEquals when qualifying the database name

[Earlopain]

And Rails/WhereNot/Rails/WhereRange as well. Fixes #1340

I'd like to extract some of this logic to a module sometime since it is looking rather similar.

The original issue mentions Redshift, and I know that MSSQL allows cross-database queries as well

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[koic]

Looks good to me!