Implement NativeMemory (#54006)

Implement NativeMemory (#54006)

* Implement NativeMemory

* Exposing additional APIs as approved

* Ensure we have a test covering alignment and size being less than sizeof(void*)

* Update src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeMemory.Unix.cs

Co-authored-by: Jan Kotas <jkotas@microsoft.com>
* Responding to PR feedback

* Adding additional alignment test coverage for 1 to 16384

* Add coverage for 65k and 1/2/4MB alignments

* Fixing the Native\Unix\System.Native\CMakeLists.txt

* Update src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeMemory.Unix.cs

Co-authored-by: Jan Kotas <jkotas@microsoft.com>
* Don't call Buffer.Memmove in NativeMemory.AlignedRealloc if ptr is null

* Updating NativeMemory.AlignedRealloc to correctly copy only the size of the last allocation

* Ensure check_symbol_exists(HAVE_ALIGNED_ALLOC) is under the non-apple paths

* Check for malloc_usable_size in malloc_np for FreeBSD and ensure tests compile

* Fix the ReallocSmallerToLargerTest test

* Handle that posix_memalign differs from aligned_alloc for size == 0

Co-authored-by: Jan Kotas <jkotas@microsoft.com>