Update provider_compute_event_enable_mask so EventSouces with no keywords show up by default (#75248)

Author: davmason

src/native/eventpipe/ep-provider.c

@@ -245,6 +245,16 @@ ep_provider_add_event (
 
 	ep_requires_lock_not_held ();
 
+	// Keyword bits 44-47 are reserved for use by EventSources, and every EventSource sets them all.
+	// We filter out those bits here so later comparisons don't have to take them in to account. Without
+	// filtering, EventSources wouldn't show up with Keywords=0.
+	uint64_t session_mask = ~0xF00000000000;
+	// -1 is special, it means all keywords. Don't change it.
+	uint64_t all_keywords = (uint64_t)(-1);
+	if (keywords != all_keywords) {
+		keywords &= session_mask;
+	}
+
 	EventPipeEvent *instance = ep_event_alloc (
 		provider,
 		keywords,