feat: multichoice

[pscott]

Add support for multichoice

This PR adds support for for multichoice (i.e not only for / against / abstain). This PR does not add support for weighted voting or ranked choice.

The way multichoice is added here is instead of having fixed 0/1/2 choice, we now have an Array of choices. Upon proposal creation, a number of choices is passed in to specify the number of choices possible for this proposal.

Interface changes

The execute function of a voting strategy replaces votes_for, votes_against, votes_abstain by a single array votes.
The same goes for get_proposal_status.
The vote_power takes a u128 instead of an enum. Same goes for fn vote on the space contract.
The propose function on the space contract now takes a choices: u128 parameter that represents the number of choices. Same goes for the update_proposal function.

Typehashes for signature are modified see starknet/src/utils/constants.cairo.
The choice enum has been removed from the code.

Note

Although the execution strategy now takes votes[] as an array, it doesn't mean it should support any number of choices. For example, the l1 avatar executions strategy still uses a simple quorum, and will treat the votes[] array as an array of 3 elements, containing for / against / abstain votes.