Key Rotation for Tracked Signing Keys

As required in the Community & Coinholder ZIP, we need a mechanism to rotate the Key-Holder Organizations' disbursement authorization key for the Coinholder-Controlled Fund. This key will initially be hard-coded into the consensus rules, and there needs to be some transaction-based mechanism to rotate it.

It would also be beneficial for this mechanism to support future rotation of ZSA Issuer keys (which are also "hard-coded" into consensus by the first transaction containing an issuance bundle authorized by an ik).