filter with `'pg_class'::regclass` produces `relation "pg_class" does not exist` error when `Eval` is called during `simplifyFilters`

[angelamayxie]

simplifyFilters is an optimization rule in gms that calls Eval on any filter expressions that don't reference fields, unresolved columns, bind vars, or procedure params to reduce the number of Eval calls made later on.

In Doltgres, the following query produces a relation "pg_class" does not exist error
SELECT d.description from pg_catalog.pg_description d WHERE d.classoid='pg_class'::regclass

This error is produced when Eval is called on 'pg_class'::regclass (this is an ExplicitCast expression that casts a Literal)

Skipped tests added in #2218