Query Service: Combine SSE handling in single tenant and multi tenant paths (#108041)

* parse via sse

I need to figure out how to handle the pipeline.execute with our own
client. I think this is important for MT reasons, just like using our
own cache (via legacy) is important.

parsing is done though!

* WIP nonsense

* horrible code but i think it works

* Add support for sql expressions config settings

* Cleanup:
- remove spew from nodes.go
- uncomment out plugin context and use in single tenant flow
- make code more readable and add comments

* Cleanup:
- create separate file for mt ds client builder
- ensure error handling is the same for both expressions and regular queries
- other cleanup

* not working but good thoughts

* WIP, vector not working for non sse

* super hacky but i think vectors work now

* delete delete delete

* Comments for future ref

* break out query handling and start test

* add prom debugger

* clean up: remove comments and commented out bits

* fix query_test

* add prom debugger

* create table-driven tests with testsdata files

* Fix test

* Add test

* go mod??

* idk

* Remove comment

* go enterprise issue maybe

* Fix codeowners

* Delete

* Remove test data

* Clean up

* logger

* Remove go changes hopefully

* idk go man

* sad

* idk i ran go mod tidy and this is what it wants

* Fix readme, with much help from adam

* some linting and testing errors

* lint

* fix lint

* fix lint register.go

* another lint

* address lint in test

* fix dead code and linters for query_test

* Go mod?

* Struggling with go mod

* Fix test

* Fix another test

* Revert headers change

* Its difficult to test this in OSS as it depends on functionality defined in enterprise, let's bring these tests back in some form in enterprise

* Fix codeowners

---------

Co-authored-by: Adam Simpson <adam@adamsimpson.net>

pkg/api/ds_query_test.go

@@ -22,6 +22,7 @@ import (
 	"github.com/grafana/grafana/pkg/plugins/manager/registry"
 	"github.com/grafana/grafana/pkg/services/datasources"
 	fakeDatasources "github.com/grafana/grafana/pkg/services/datasources/fakes"
+	"github.com/grafana/grafana/pkg/services/mtdsclient"
 	"github.com/grafana/grafana/pkg/services/pluginsintegration/pluginconfig"
 	"github.com/grafana/grafana/pkg/services/pluginsintegration/plugincontext"
 	pluginSettings "github.com/grafana/grafana/pkg/services/pluginsintegration/pluginsettings/service"
@@ -60,16 +61,27 @@ func TestAPIEndpoint_Metrics_QueryMetricsV2(t *testing.T) {
 				return &backend.QueryDataResponse{Responses: resp}, nil
 			},
 		},
-		plugincontext.ProvideService(cfg, localcache.ProvideService(), &pluginstore.FakePluginStore{
-			PluginList: []pluginstore.Plugin{
-				{
-					JSONData: plugins.JSONData{
-						ID: "grafana",
+		plugincontext.ProvideService(
+			cfg,
+			localcache.ProvideService(),
+			&pluginstore.FakePluginStore{
+				PluginList: []pluginstore.Plugin{
+					{
+						JSONData: plugins.JSONData{
+							ID: "grafana",
+						},
 					},
 				},
 			},
-		}, &fakeDatasources.FakeCacheService{}, &fakeDatasources.FakeDataSourceService{},
-			pluginSettings.ProvideService(dbtest.NewFakeDB(), secretstest.NewFakeSecretsService()), pluginconfig.NewFakePluginRequestConfigProvider()),
+			&fakeDatasources.FakeCacheService{},
+			&fakeDatasources.FakeDataSourceService{},
+			pluginSettings.ProvideService(
+				dbtest.NewFakeDB(),
+				secretstest.NewFakeSecretsService(),
+			),
+			pluginconfig.NewFakePluginRequestConfigProvider(),
+		),
+		mtdsclient.NewNullMTDatasourceClientBuilder(),
 	)
 	server := SetupAPITestServer(t, func(hs *HTTPServer) {
 		hs.queryDataService = qds
@@ -252,6 +264,7 @@ func TestDataSourceQueryError(t *testing.T) {
 						&fakeDatasources.FakeCacheService{}, ds,
 						pluginSettings.ProvideService(dbtest.NewFakeDB(),
 							secretstest.NewFakeSecretsService()), pluginconfig.NewFakePluginRequestConfigProvider()),
+					mtdsclient.NewNullMTDatasourceClientBuilder(),
 				)
 				hs.QuotaService = quotatest.New(false, nil)
 			})