apple/macii.cpp: Cleanup pass and RAM support improvements [R. Belmont]

- Properly emulate how the GLUE ASIC lays out memory.
- All RAM sizes that were valid on hardware now work, and sizes >8 MiB that caused
  the original Mac II ROM to malfunction are locked out for that machine
- Modernized types, usage, and class organization
- Removed model-specific runtime checks

Author: rb6502