Project cleanup

[tilk]

There is a need to move stuff around to make things more intuitive for newcomers (and others). Some problems in directory organization are:

• The coreblocks/params directory is a mess. It was supposed to contain things related to parametrization (at the beginning, mostly GenParams). Now it also contains:
  • dependencies - the dependency manager,
  • keys - the dependency keys (which we agreed to have in one place),
  • isa and instr - RISC-V architecture related things,
  • optypes - our internal encoding of instructions, which is entangled with ISA, decoding and FUs.
• The structs_common directory somehow contains a CSR unit. The directory was meant to contain implementation of data structures, i.e. things that are shared between components.
• The coreblocks/transactions/lib file is one big ball of stuff, it should finally be split.
• The stages directory is weird, it contains:
  • The announcement module, in a file which is somehow named backend,
  • The retirement stage,
  • Abstractions related to functional units/blocks.

There are potentially other issues I can't remember right now, please write them down in comments.