Tracking issue for RFC 45: Move `hdl.Memory` to `lib.Memory`

[whitequark]

• RFC PR: Move hdl.memory to lib.memory and extend it rfcs#45
• Implementation PR: Implement RFC 45: Move hdl.Memory to lib.Memory. #1142
• Documentation PR: Finish lib.memory documentation #1228
• Removal PR: hdl: remove Memory. #1395