Various createdump fixes. Smaller MacOS dump size, better logging/stats, misc cleanup...

Various createdump fixes. Smaller MacOS dump size, better logging/stats, misc cleanup, etc. (#71569)

* Fix where CombineMemoryRegions is called and perf fix for PAGE_SIZE on MacOS M1

* Remove MEMORY_REGION_FLAG_MEMORY_BACKED flags because it was always set now

* Add better memory tracing and memory region stats

Fix MacOS native module regions when overlapping with existing.

Fix MacOS adding the managed modules to the module mapping list before the "other mappings" is built.

* Don't add share_mode == SM_EMPTY regions

* Add crashreport success status message for VS4Mac

* Launch createdump from SIGTERM handler directly to reduce the time it takes to get the crash report/dump for VS4Mac

* Fix issue https://github.com/dotnet/runtime/issues/71561

* Add target process terminated/alive message

* Add total createdump elapsed time message