MM-43144: Add teams loader (#19960)

```release-note
NONE
```

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/graphql.go

@@ -65,6 +65,7 @@ const (
 	webCtx            ctxKey = 0
 	rolesLoaderCtx    ctxKey = 1
 	channelsLoaderCtx ctxKey = 2
+	teamsLoaderCtx    ctxKey = 3
 )
 
 const loaderBatchCapacity = 200
@@ -107,6 +108,9 @@ func (api *API) graphQL(c *Context, w http.ResponseWriter, r *http.Request) {
 	channelsLoader := dataloader.NewBatchedLoader(graphQLChannelsLoader, dataloader.WithBatchCapacity(loaderBatchCapacity))
 	reqCtx = context.WithValue(reqCtx, channelsLoaderCtx, channelsLoader)
 
+	teamsLoader := dataloader.NewBatchedLoader(graphQLTeamsLoader, dataloader.WithBatchCapacity(loaderBatchCapacity))
+	reqCtx = context.WithValue(reqCtx, teamsLoaderCtx, teamsLoader)
+
 	response = api.schema.Exec(reqCtx,
 		params.Query,
 		params.OperationName,