SQL Expressions: Rework backend errors and error instrumentation (#109633)

* Capture error_type label on metrics/traces
* Make error messages more helpful to user
* Use errutil, categorized errors, and tie them to error_type (category in code)
* Misc trace fixes
* Add metric to track SQL input conversion

pkg/expr/sql/parser_allow_test.go

@@ -95,7 +95,7 @@ func TestAllowQuery(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			_, err := AllowQuery(tc.q)
+			_, err := AllowQuery("A", tc.q)
 			if tc.err != nil {
 				require.Error(t, err)
 			} else {