Support "major" protocol version deprecation logic

[antiochp]

We want the ability to be able to "deprecate" old protocol versions.

This rules around this are specified here - https://github.com/mimblewimble/docs/wiki/P2P-Protocol#phasing-out-old-peers

Proposal related to HF4 is here - https://github.com/mimblewimble/grin/issues/3430 Related PR proposed for 4.1.0 - https://github.com/mimblewimble/grin/pull/3434

The "major version" logic is not currently implemented. We should implement this and ensure we have good test coverage around it.