Merge pull request #2449 from lambdageek/dev/no-chunks

[handle] Remove chunk_last field from MonoHandleArena

Remove the `chunk_last` field.  This changes MonoHandleArena from a queue of chunks to a stack of chunks.  More importantly, the MonoHandleArena has an initial chunk that is allocated on the stack together with the arena.  Previously that chunk was at the front of the list of chunks, but now it is at the end.