Optimize `mtree_set` and `mtree_cwm`

[hackaugusto]

As part of https://github.com/0xPolygonMiden/miden-vm/issues/646 and https://github.com/0xPolygonMiden/miden-vm/issues/653 the instructions mtree_set and mtree_cwm had their output formats changed.

This was done via the assembler, which introduces a couple of new core vm opcode for each of the mtree_set and mtree_cwm instructions. This issue is for optimizing those.

Follow up to https://github.com/0xPolygonMiden/miden-vm/pull/652#pullrequestreview-1266746611