chore: add profiling labels for pprof analysis (#19232)

PProf labels segment the code into groups for determing the source of
cpu/memory profiles. Since the web server and background jobs share a
lot of the same code (eg wsbuilder), it helps to know if the load is
user induced, or background job based.

coderd/coderd.go

@@ -852,6 +852,7 @@ func New(options *Options) *API {
 
 	r.Use(
 		httpmw.Recover(api.Logger),
+		httpmw.WithProfilingLabels,
 		tracing.StatusWriterMiddleware,
 		tracing.Middleware(api.TracerProvider),
 		httpmw.AttachRequestID,