feat: support CreateCastStmt

[cvng]

What kind of change does this PR introduce?

feat: support CreateCastStmt

What is the current behavior?

Parser panics

What is the new behavior?

[2023-12-13T14:38:21Z DEBUG parser::codegen::tests] pg_query_root: Some( CreateCastStmt( CreateCastStmt { sourcetype: Some( TypeName { names: [ Node { node: Some( String( String { sval: "pg_catalog", }, ), ), }, Node { node: Some( String( String { sval: "int8", }, ), ), }, ], type_oid: 0, setof: false, pct_type: false, typmods: [], typemod: -1, array_bounds: [], location: 13, }, ), targettype: Some( TypeName { names: [ Node { node: Some( String( String { sval: "int4", }, ), ), }, ], type_oid: 0, setof: false, pct_type: false, typmods: [], typemod: -1, array_bounds: [], location: 23, }, ), func: None, context: CoercionAssignment, inout: true, }, ), )

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