Remove sleeps and timed polling from networking

Socket waits now block in select() on the socket plus a wake or cancel
socket (Common/Net/Cancel), so a stop or cancel ends them at once.

- HTTP: cancel flags become net::CancelToken; Connect waits once on all
  addresses, receives wait instead of spinning, no DNS retry sleep.
- Adhoc: the friend finder and adhoc server block on their sockets with
  a wake socket and a deadline; matching runs on a CoreTiming tick
  instead of two threads (savestate section bumped).
- sceNetInet select/poll check without blocking and park the HLE thread,
  re-checked from a CoreTiming event until ready or the emulated
  timeout.
- Vendor the aemu_postoffice client (was a submodule) with no sleeps:
  waits on the socket, close via shutdown and an eventcount, cancelable
  connects, and lock-free session slot claims.
- PortManager waits without a timeout; PSP_InitWait replaces the
  headless boot poll.
- TimeUtil: sleep_us/sleep_ms only outside the core; sleep_precise,
  sleep_random, yield and the Windows timer period are gone.
- Unit test for the socket waits.

Common/Net/HTTPNaettRequest.cpp

@@ -16,7 +16,7 @@
 namespace http {
 
 HTTPSRequest::HTTPSRequest(RequestMethod method, std::string_view url, std::string_view postData, std::string_view postMime, const Path &outfile, RequestFlags flags, std::string_view name)
-	: Request(method, url, name, outfile, &cancelled_, flags), postData_(postData), postMime_(postMime) {
+	: Request(method, url, name, outfile, flags), postData_(postData), postMime_(postMime) {
 }
 
 HTTPSRequest::~HTTPSRequest() {
@@ -82,7 +82,7 @@ void HTTPSRequest::Start() {
 	// it once it finishes.
 	sink_ = std::make_unique<NaettBodySink>();
 	// In case someone managed to cancel us between construction and here.
-	sink_->cancelled = cancelled_;
+	sink_->cancelled = IsCancelled();
 	sink_->postData = postData_;
 
 	std::vector<naettOption *> options;