IF: Add the activation of WTMSIG_BLOCK_SIGNATURES and ACTION_RETURN_VALUE features as prerequisite for the activation of the instant_finality feature

[systemzax]

INSTANT_FINALITY should have prerequisite:

• ACTION_RETURN_VALUE is desired so that the IBC contract can use it. Also it changes the algorithm for digest computation and don't want IBC to have to handle both ways.
• WTMSIG_BLOCK_SIGNATURES Changes the algorithm for digest computation and don't want the IBC to handle both ways. Also we do not need to check if WTMSIG_BLOCK_SIGNATURES is activated in block_header_state::next.
• DISALLOW_EMPTY_PRODUCER_SCHEDULE Using the same set_proposed_producers which checks this protocol feature. We do not want empty proposer schedules.

[heifner]

I wonder if it is useful to draw a line in the sand and make INSTANT_FINALITY depend on all previous protocol features. Going forward all new protocol features could depend on INSTANT_FINALITY. If we ever mint a new genesis we could clean up all the existing protocol feature differences.

[greg7mdp]

Should we also make INSTANT_FINALITY depend on BLS_PRIMITIVES2 and WEBAUTHN_KEY which I believe are required for the BIOS contract?

Areg: yes for BLS_PRIMITIVES2