EventPipe container types optimizations. (dotnet#83251)

During work collecting regressions statistics for dotnet#78852 I did some profiling on performance tests included in native EventPipe tests, https://github.com/dotnet/runtime/blob/main/src/mono/mono/eventpipe/test. This commit implements a couple of optimizations in the EventPipe native container classes as well as Mono's EventPipe implementation improving performance in low level native EventPipe performance tests.

Commit also includes a number of new native EventPipe tests covering optimizations done in dn_vector_ptr_t.

src/mono/mono/eventpipe/ep-rt-mono.h

@@ -1063,9 +1063,10 @@ uint8_t *
 ep_rt_valloc0 (size_t buffer_size)
 {
 	uint8_t *buffer = (uint8_t *)mono_valloc (NULL, buffer_size, MONO_MMAP_READ | MONO_MMAP_WRITE, MONO_MEM_ACCOUNT_PROFILER);
-
-	if (buffer)
-		memset (buffer, 0, buffer_size);
+#ifdef EP_CHECKED_BUILD
+	for (size_t i = 0; i < buffer_size; i++)
+		EP_ASSERT (buffer [i] == 0);
+#endif
 	return buffer;
 }