Add complete test method overrides with proper SQL assertions

- Added Final_GroupBy_TagWith override to NorthwindGroupByQueryMySqlTest.cs with MySQL SQL
- Added Where_simple_closure override to NorthwindWhereQueryMySqlTest.cs with MySQL SQL
- Both methods now pass Check_all_tests_overridden validation
- All related tests pass successfully

Co-authored-by: renemadsen <[email protected]>

Author: Copilot

test/EFCore.MySql.FunctionalTests/Query/NorthwindGroupByQueryMySqlTest.cs

@@ -3796,7 +3796,14 @@ public override async Task Final_GroupBy_TagWith(bool async)
         {
             await base.Final_GroupBy_TagWith(async);
 
-            AssertSql();
+            AssertSql(
+"""
+-- foo
+
+SELECT `c`.`City`, `c`.`CustomerID`, `c`.`Address`, `c`.`CompanyName`, `c`.`ContactName`, `c`.`ContactTitle`, `c`.`Country`, `c`.`Fax`, `c`.`Phone`, `c`.`PostalCode`, `c`.`Region`
+FROM `Customers` AS `c`
+ORDER BY `c`.`City`
+""");
         }
 
         [ConditionalFact]

test/EFCore.MySql.FunctionalTests/Query/NorthwindWhereQueryMySqlTest.cs

@@ -513,11 +513,20 @@ public override async Task Where_simple(bool async)
 
         }
 
-        public override void Where_simple_closure()
+        public override async Task<string> Where_simple_closure(bool async)
         {
-            base.Where_simple_closure();
+            var result = await base.Where_simple_closure(async);
 
-            AssertSql();
+            AssertSql(
+"""
+@city='London' (Size = 15)
+
+SELECT `c`.`CustomerID`, `c`.`Address`, `c`.`City`, `c`.`CompanyName`, `c`.`ContactName`, `c`.`ContactTitle`, `c`.`Country`, `c`.`Fax`, `c`.`Phone`, `c`.`PostalCode`, `c`.`Region`
+FROM `Customers` AS `c`
+WHERE `c`.`City` = @city
+""");
+            
+            return result;
         }
 
         public override async Task Where_indexer_closure(bool async)