[sBTC] Add minimal contract to allow token and key administration

[xoloki]

Is your feature request related to a problem? Please describe.
For sBTC we need a way to administer tokens and keys for the signers

Describe the solution you'd like
Add a minimal clarity contract that does this

Describe alternatives you've considered
There isn't any other way of doing this that will allow the interaction we need

Additional context
member fields:
signers public keys
coordinator public key
admins (2-of-3) 3 admin keys
admin methods
at beginning, contract needs to be init(admin principals) by owner.
mutate signers, coordinator, admins
coordinator method gated by a frost signature
peg-in (mint)
open methods
withdrawal request (peg-out)

manages signer membership
contract could have a multi-sig admin
maintains public keys for signers and coordinator

[jcnelson]

Once CI passes on #3499 we can merge it and close this.