Catherine: actually, what do you think about this proposal for RFC 62 amendment:

- `MemoryData` grows `__getitem__`, which returns either `MemoryRow` (single item) or `MemorySlice`
- `sim.memory_read` and `sim.memory_write` are removed
- `sim.get` is made to accept `MemoryData` (returns the whole thing as a tuple), `MemorySlice` (returns a tuple), `MemoryRow` (returns a single int / `from_bits`)
- `sim.set` likewise accepts `MemoryData` and `MemorySlice` (value must be an interable of matching size), and `MemoryRow`
- `sim.changed` accepts `MemoryData`, `MemorySlice`, `MemoryRow`; for `MemoryRow`, behavior is as if it was a signal; for the other two, you get a dict of `{address: new_value}` containing only the changed elements
- `sim.tick.sample` from your proposal likewise accepts those three, same semantics as `sim.get`
- `traces` likewise accepts `MemoryData`, `MemorySlice`, `MemoryRow`