ICS4: Optimal behaviour for incompatible crossing hello with unequal sequences

[AdityaSripal]

Currently if there are crossing hellos of incompatible upgrades with unequal sequences.

The TRY will be explicitly rejected on both sides due to an earlier compatibility check before the sequencing logic can write an error receipt.

This then will require an explicit reset by one of the parties to continue the handshake.

One alternative approach could be to instead do the sequencing check first and error out the lower sequence incompatible upgrade.

[sangier]

Thanks for this catch! The alternative approach LGTM!