[compiler] Fix codegen for nested method calls with memoized properties

When processing nested method calls like `Math.floor(diff.bar())`, the compiler would trigger an invariant that `MethodCall::property must be a MemberExpression but got an Identifier`.

The issue occurred when the property (e.g., Math.floor) was memoized in a reactive scope and promoted to a named identifier. Later during codegen, retrieving this memoized temporary would return just an Identifier instead of the expected MemberExpression.

The fix handles this case by checking if the property has been memoized as an Identifier and using it directly for the call expression, rather than requiring it to be a MemberExpression.

This fixes two test cases that were previously failing.