[lsan] Bump the thread limit from 1<<13 to 1<<22

[MaskRay]

Summary

This matches asan. Some applications need more than 1<<13 threads.

compiler-rt/lib/lsan/lsan_thread.cpp

 
 static ThreadRegistry *thread_registry;
 
 static ThreadContextBase *CreateThreadContext(u32 tid) {
   void *mem = MmapOrDie(sizeof(ThreadContext), "ThreadContext");
   return new (mem) ThreadContext(tid);
 }
 
-static const uptr kMaxThreads = 1 << 13;
+static const uptr kMaxThreads = 1 << 22;  // 4M
 static const uptr kThreadQuarantineSize = 64;
 
 void InitializeThreadRegistry() {
   static ALIGNED(64) char thread_registry_placeholder[sizeof(ThreadRegistry)];
   thread_registry = new (thread_registry_placeholder)
       ThreadRegistry(CreateThreadContext, kMaxThreads, kThreadQuarantineSize);
 }