feat(cubesql): Support trivial casts in member pushdown (cube-js#9480)

This should allow pushing down expressions like `CAST(dimension AS TEXT) AS alias` into `CubeScan` as regular dimensions.
And that, in turn, should allow `__cubeJoinField` joins to see more `CubeScan`s

Supporting changes:

Remove unused rule for member pushdown from `AllMembers`
All matching happening with `CubeScanMembers` on top of actual members node, and this rule does not expect that
`member_name_to_expr` part of analysis can extract members from `CubeScanMembers(AllMembers)`, so there's no reason to keep this rule

Add explicit type in `var!` macro, to avoid type confusion.

Author: mcheshkov

rust/cubesql/cubesql/src/compile/mod.rs

@@ -13429,7 +13429,7 @@ ORDER BY "source"."str0" ASC
         V1LoadResultAnnotation::new(json!([]), json!([]), json!([]), json!([]))
     }
 
-    fn simple_load_response(data: Vec<serde_json::Value>) -> V1LoadResponse {
+    pub(crate) fn simple_load_response(data: Vec<serde_json::Value>) -> V1LoadResponse {
         V1LoadResponse::new(vec![V1LoadResult::new(empty_annotation(), data)])
     }
 

rust/cubesql/cubesql/src/compile/rewrite/mod.rs

@@ -560,7 +560,7 @@ macro_rules! var_list_iter {
 #[macro_export]
 macro_rules! var {
     ($var_str:expr) => {
-        $var_str.parse().unwrap()
+        $var_str.parse::<::egg::Var>().unwrap()
     };
 }