Address godeltaprof/http/pprof side effects and configurations

[korniltsev]

When godeltaprof/http/pprof is imported we unconditionally register endpoints into a global default mux.

pyroscope-go/godeltaprof/http/pprof/pprof.go

Lines 23 to 28 in 8003d94

	func init() {
	prefix := routePrefix()
	http.HandleFunc(prefix+"/debug/pprof/delta_heap", Heap)
	http.HandleFunc(prefix+"/debug/pprof/delta_block", Block)
	http.HandleFunc(prefix+"/debug/pprof/delta_mutex", Mutex)
	}

Some users may not want that or may do this only in some cases deciding at runtime.

Another problem with that approach is that the registered profilers are not configurable - if we introduce any configuration knobs to the profilers - it is impossible to pass them with the current approach.

We may consider creating a new http/pprof/v2 package that does not register to default mux and allows configuring the profilers