Tracking issue for RFC 62: The `MemoryData` class.

[wanda-phi]

• RFC PR: RFC 62: The MemoryData class. rfcs#62
• Implementation:
  • MemoryData class: hdl._mem: add MemoryData class. #1256
  • MemoryData._Row class: hdl._mem: implement MemoryData._Row from RFC 62. #1271
  • Documentation: Document RFC 62 #1294

[whitequark]

We need some documentation; at least, enough to know that to manipulate memory rows in simulation you need to do e.g. memory.data[0].eq(1). Currently memory.data is completely undocumented.