Explore: Queries the datasource once per run query and uses DataStreamObserver (#17263)

* Refactor: Removes replaceUrl from actions

* Refactor: Moves saveState thunk to epic

* Refactor: Moves thunks to epics

* Wip: removes resulttype and queries once

* Refactor: LiveTailing uses observer in query

* Refactor: Creates epics folder for epics and move back actioncreators

* Tests: Adds tests for epics and reducer

* Fix: Checks for undefined as well

* Refactor: Cleans up previous live tailing implementation

* Chore: merge with master

* Fix: Fixes url issuses and prom graph in Panels

* Refactor: Removes supportsStreaming and adds sockets to DataSourcePluginMeta instead

* Refactor: Changes the way we create TimeSeries

* Refactor: Renames sockets to streaming

* Refactor: Changes the way Explore does incremental updates

* Refactor: Removes unused method

* Refactor: Adds back Loading indication

pkg/plugins/datasource_plugin.go

@@ -29,6 +29,7 @@ type DataSourcePlugin struct {
 	BuiltIn       bool              `json:"builtIn,omitempty"`
 	Mixed         bool              `json:"mixed,omitempty"`
 	Routes        []*AppPluginRoute `json:"routes"`
+	Streaming     bool              `json:"streaming"`
 
 	Backend    bool   `json:"backend,omitempty"`
 	Executable string `json:"executable,omitempty"`