pkg/sql/sqlstats: de-flake TestTransactionInsightsFailOnCommit

Fixes: #117061

TestTransactionInsightsFailOnCommit runs two transactions, one
of which is expected to fail on commit due to an isolation error
as it interacts with the other transaction.

We query crdb_internal.node_txn_execution_insights, which queries
the in-memory insights data, to check that a txn insight was generated
for the failed txn with a `FailedExecution` insight.

However, when querying the crdb_internal table, the query is too broad.
In the test, the successful transaction can still possibly generate a
`SlowExecution` insight. In this case, when looking for the
`FailedExecution` insight, we were instead getting an insight from the
successful transaction.

The fix is to narrow the SELECT criteria to ensure we're selecting the
correct insight.

The fix also expands the failed assertion logging.

Release note: none

pkg/sql/sqlstats/insights/integration/insights_test.go

@@ -490,12 +490,16 @@ SELECT query,
        COALESCE(last_error_code, '') last_error_code,
        COALESCE(last_error_redactable, '') last_error
 FROM crdb_internal.node_txn_execution_insights 
-WHERE app_name = $1`, appName)
+WHERE app_name = $1
+AND query = 'SELECT * FROM myusers WHERE city = _ ; UPDATE myusers SET name = _ WHERE city = _'`, appName)
 
 					return row.Scan(&query, &problems, &status, &errorCode, &errorMsg)
 				})
 
-				require.Equal(t, "SELECT * FROM myusers WHERE city = _ ; UPDATE myusers SET name = _ WHERE city = _", query)
+				require.Equalf(t,
+					"SELECT * FROM myusers WHERE city = _ ; UPDATE myusers SET name = _ WHERE city = _", query,
+					"unexpected txn insight found - query: %s, problems: %s, status: %s, errCode: %s, errMsg: %s",
+					query, problems, status, errorCode, errorMsg)
 				expectedProblem := "{FailedExecution}"
 				replacedSlowProblems := problems
 				if problems != expectedProblem {