SQL Expressions: Re-implement feature using go-mysql-server (#99521)

* Under feature flag `sqlExpressions` and is experimental
* Excluded from arm32
* Will not work with the Query Service yet
* Does not have limits in place yet
* Does not working with alerting yet
* Currently requires "prepare time series" Transform for time series viz
 
---------

Co-authored-by: Sam Jewell <sam.jewell@grafana.com>

pkg/expr/sql/parser_allow_test.go

@@ -0,0 +1,80 @@
+package sql
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestAllowQuery(t *testing.T) {
+	testCases := []struct {
+		name string
+		q    string
+		err  error
+	}{
+		{
+			name: "a big catch all for now",
+			q:    example_metrics_query,
+			err:  nil,
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := AllowQuery(tc.q)
+			if tc.err != nil {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
+var example_metrics_query = `WITH
+  metrics_this_month AS (
+    SELECT
+      Month,
+      namespace,
+      sum(BillableSeries) AS billable_series
+    FROM metrics
+    WHERE
+      Month = "2024-11"
+    GROUP BY 
+      Month,
+      namespace
+    ORDER BY billable_series DESC
+  ),
+  total_metrics AS (
+    SELECT SUM(billable_series) AS metrics_billable_series_total
+    FROM metrics_this_month
+  ),
+  total_traces AS (
+    -- "usage" is a reserved keyword in MySQL. Quote it with backticks.
+    SELECT SUM(value) AS traces_usage_total
+    FROM traces
+  ),
+  usage_by_team AS (
+    SELECT
+      COALESCE(teams.team, 'unaccounted') AS team,
+      1 + 0 AS team_count,
+      -- Metrics
+      SUM(COALESCE(metrics_this_month.billable_series, 0)) AS metrics_billable_series,
+      -- Traces
+      SUM(COALESCE(traces.value, 0)) AS traces_usage
+    -- FROM teams
+    -- FULL OUTER JOIN metrics_this_month
+    FROM metrics_this_month
+    FULL OUTER JOIN teams
+      ON teams.namespace = metrics_this_month.namespace
+    FULL OUTER JOIN traces
+      ON teams.namespace = traces.namespace
+    GROUP BY
+      -- COALESCE(teams.team, 'unaccounted')
+      teams.team
+    ORDER BY metrics_billable_series DESC
+  )
+
+SELECT *
+FROM usage_by_team
+CROSS JOIN total_metrics
+CROSS JOIN total_traces`