feat(prometheus): add metrics to Subsonic API and Plugins (#4266)

* Add prometheus metrics to subsonic and plugins

* address feedback, do not log error if operation is not supported

* add missing timestamp and client to stats

* remove .view from subsonic route

* directly inject DataStore in Prometheus, to avoid having to pass it in every call

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>
Co-authored-by: Deluan <deluan@navidrome.org>

server/subsonic/media_retrieval_test.go

@@ -33,7 +33,7 @@ var _ = Describe("MediaRetrievalController", func() {
 			MockedMediaFile: mockRepo,
 		}
 		artwork = &fakeArtwork{data: "image data"}
-		router = New(ds, artwork, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
+		router = New(ds, artwork, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
 		w = httptest.NewRecorder()
 		DeferCleanup(configtest.SetupConfig())
 		conf.Server.LyricsPriority = "embedded,.lrc"