Serialize cluster into yaml

[pjanevskiTT]

Issue

Solving part of #431

Description

Add a function to serialize cluster to the yaml (reverse of what we were doing so far). Add flag to all Cluster constructors to create mock chips inside Cluster if user wants that. Expose this (de)serializing through the API as mentioned in the issue above. Output yaml look like (note the styling difference than original, but in YAML world it is the same)

arch:
  1: wormhole_b0
  0: wormhole_b0
ethernet_connections:
  -
    - chip: 1
      chan: 1
    - chip: 0
      chan: 9
  -
    - chip: 1
      chan: 0
    - chip: 0
      chan: 8
chips_with_mmio:
  - 0: 0
harvesting:
  1:
    noc_translation: true
    harvest_mask: 513
  0:
    noc_translation: true
    harvest_mask: 129
boardtype:
  1: n300
  0: n300 

List of the changes

• Add serialize function to Cluster (public)
• Add serialize function cluste descriptor (not public)
• Add flag to all Cluster constructors to create mock chips
• Add a test

Testing

CI + new test

API Changes

Added create_mock_chips to Cluster constuctors, but changes not needed in UMD clients.

[pjanevskiTT]

@cfjchu can you check whether this API would satisfy your requirements. Next step is going to be expanding cluster yaml with all the info needed. But I think we can fix the API now

[pjanevskiTT]

@broskoTT fyi, skip_driver_allocs had the same purpose as create_mock_chips. I renamed it and fixed few bugs which we had when creating mock chips. You can take a look at 516d5ec if you want