[Handshake] Use symbols instead of id integer attributes for memories

All handshake memories must currently have an `id` integer attribute. To no surprise, this is used to unique each handshake memory.
Issues with this:
1. No logic is implemented to assert that id's are actually unique
2. The `id`s should be replaced with symbols (in other words, memories should be named). This will also help lowerings, which nevertheless are forced to come up with some unique name for the memory (currently based on the id).

Start by locating the Handshake memory definitions and the lowerings that currently derive names from integer ids. Trace how memory ids are represented and consumed, then determine the affected checks and tests; done means memories use symbols consistently and lowerings no longer need to generate names from ids.

Written by the indexing model from the issue text.