Chore: Refactor usage of legacy data contracts (#41218)

Refactor usage of legacy data contracts. Moves legacy data contracts 
to pkg/tsdb/legacydata package.
Refactor pkg/expr to be a proper service/dependency that can be provided 
to wire to remove some unneeded dependencies to SSE in ngalert and other places.
Refactor pkg/expr to not use the legacydata,RequestHandler and use 
backend.QueryDataHandler instead.

pkg/tsdb/cloudwatch/request_parser_test.go

@@ -6,7 +6,7 @@ import (
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana/pkg/components/simplejson"
-	"github.com/grafana/grafana/pkg/tsdb"
+	"github.com/grafana/grafana/pkg/tsdb/legacydata"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -48,7 +48,7 @@ func TestRequestParser(t *testing.T) {
 		})
 	})
 
-	timeRange := tsdb.NewTimeRange("now-1h", "now-2h")
+	timeRange := legacydata.NewDataTimeRange("now-1h", "now-2h")
 	from, err := timeRange.ParseFrom()
 	require.NoError(t, err)
 	to, err := timeRange.ParseTo()
@@ -138,7 +138,7 @@ func TestRequestParser(t *testing.T) {
 			"hide":      false,
 		})
 		query.Set("period", "900")
-		timeRange := tsdb.NewTimeRange("now-1h", "now-2h")
+		timeRange := legacydata.NewDataTimeRange("now-1h", "now-2h")
 		from, err := timeRange.ParseFrom()
 		require.NoError(t, err)
 		to, err := timeRange.ParseTo()