Change primitives to match guide's description of candidate types

[rphmeier]

Might have a bit of fallout in runtime/common, validation, and network, but shouldn't be too much.

Some other concrete updates:

• InclusionInherent::inclusion needs to take the candidate commitments alongside the abridged candidate receipt
• Inclusion::process_candidates needs to check that the encoded commitments match the hash in the abridged receipt.
• Inclusion should store commitments in a separate map alongside the PendingAvailability, since they may be large. This will make bitfield processing more efficient for candidates that include code upgrades.