Remove some of the complexity from __timedwait.c. NFC

This should have been part of #26471.

The breaking up of the wait time for 2 of the 3 cases that are handled
here is now handled one layer own in emscripten_futex_wait:

1. Breaking up the wait because we are the main runtime thread.
2. Breaking up the wait because we are async cancelable.

The third cases here (breaking up the wait because we are cancelable
in the non-async sense) still needs to be handled here at the higher
level.

Author: sbc100

system/lib/libc/musl/src/thread/__timedwait.c

@@ -59,20 +59,16 @@ int __timedwait_cp(volatile int *addr, int val,
 
 #ifdef __EMSCRIPTEN__
 	double msecsToSleep = top ? (top->tv_sec * 1000 + top->tv_nsec / 1000000.0) : INFINITY;
-	int is_runtime_thread = emscripten_is_main_runtime_thread();
-
-	// Main runtime thread may need to run proxied calls, so sleep in very small slices to be responsive.
-	double max_ms_slice_to_sleep = is_runtime_thread ? 1 : 100;
 
 	// cp suffix in the function name means "cancellation point", so this wait can be cancelled
 	// by the users unless current threads cancelability is set to PTHREAD_CANCEL_DISABLE
 	// which may be either done by the user of __timedwait() function.
-	if (is_runtime_thread ||
-	    pthread_self()->canceldisable != PTHREAD_CANCEL_DISABLE ||
-	    pthread_self()->cancelasync) {
+	pthread_t self = pthread_self();
+	if (self->canceldisable != PTHREAD_CANCEL_DISABLE) {
+		double max_ms_slice_to_sleep = 100;
 		double sleepUntilTime = emscripten_get_now() + msecsToSleep;
 		do {
-			if (pthread_self()->cancel) {
+			if (self->cancel) {
 				// The thread was canceled by pthread_cancel().
 				// In the case of cancelasync or PTHREAD_CANCEL_ENABLE we can just call
 				// __pthread_testcancel(), which won't return at all.

test/codesize/test_codesize_minimal_pthreads.json

@@ -1,10 +1,10 @@
 {
   "a.out.js": 7364,
   "a.out.js.gz": 3607,
-  "a.out.nodebug.wasm": 19265,
-  "a.out.nodebug.wasm.gz": 8934,
-  "total": 26629,
-  "total_gz": 12541,
+  "a.out.nodebug.wasm": 19233,
+  "a.out.nodebug.wasm.gz": 8918,
+  "total": 26597,
+  "total_gz": 12525,
   "sent": [
     "a (memory)",
     "b (emscripten_get_now)",

test/codesize/test_codesize_minimal_pthreads_memgrowth.json

@@ -1,10 +1,10 @@
 {
   "a.out.js": 7766,
   "a.out.js.gz": 3812,
-  "a.out.nodebug.wasm": 19266,
-  "a.out.nodebug.wasm.gz": 8935,
-  "total": 27032,
-  "total_gz": 12747,
+  "a.out.nodebug.wasm": 19234,
+  "a.out.nodebug.wasm.gz": 8919,
+  "total": 27000,
+  "total_gz": 12731,
   "sent": [
     "a (memory)",
     "b (emscripten_get_now)",