SQL Expressions: Add JSON support (#103157)

- Support bi-directional mapping of frame JSON fields and GMS (go-mysql-server) columns 
- Permit GMS json functions

Co-authored-by: Kyle Brandt <kyle@grafana.com>

pkg/expr/sql/parser_allow.go

@@ -210,6 +210,12 @@ func allowedFunction(f *sqlparser.FuncExpr) (b bool) {
 	case "cast":
 		return
 
+	// JSON functions
+	case "json_extract", "json_unquote", "json_contains",
+		"json_object", "json_array", "json_set", "json_remove",
+		"json_length", "json_search", "json_type":
+		return
+
 	default:
 		return false
 	}