Add information to our type mappings whether the literal SQL representation defaults to the store type

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For some store types, their literal SQL representation automatically gets evaluated by the database to be that type; this is the case e.g. for int (SELECT 8 returns an int). But for others that's not the case, i.e. the literal representation of smallint is also 8, but that gets evaluated as int.

We can add a flag on our type mappings which says if the SQL literal representation maps back to the type; this could allow us to omit explicit conversions in some cases.

• When generating a VALUES expression, we add explicit conversion to make sure the right store type comes out.

Note relationship with #27150: the literal representation of bool in SQL Server is CAST(1 AS BIT), which is there to fix mitigate #24075 (projecting out), but causes perf issues. We could try to add the CAST only where needed (VALUES, when projecting out) rather than everywhere.