refactor: use dialect-neutral Jet type aliases

Replace mysql/postgres intersection interfaces with mysql type aliases
per go-jet/jet#555 and generalize Apply/Expr signatures.

Co-authored-by: Cursor <cursoragent@cursor.com>

jet_columns.go

@@ -4,14 +4,14 @@ import "github.com/go-jet/jet/v2/mysql"
 
 // NormalCols processes a list of columns and strips out any that implement any of
 // ColumnTimestamp, ColumnTime, or ColumnDate.
-func NormalCols[CL ColumnList](cols ...Column) CL {
-	res := make(CL, 0)
+func NormalCols(cols ...Column) ColumnList {
+	res := make(ColumnList, 0)
 
 	for _, col := range cols {
 		switch col.(type) {
-		case mysql.ColumnTimestamp, // = postgres.ColumnTimestamp
-			mysql.ColumnTime, // = postgres.ColumnTime
-			mysql.ColumnDate: // = postgres.ColumnDate
+		case mysql.ColumnTimestamp,
+			mysql.ColumnTime,
+			mysql.ColumnDate:
 		default:
 			res = append(res, col)
 		}