Implement missing governance proposals

[maurolacy]

The following governance proposals are currently unimplemented, as proposals that can be voted through a voting contract:

• Text. (Redundant? Already implemented at contract level)
• ChangeParams. (Done in Implement the ChangeParams proposal #157).
• IbcClientUpdate (See Add UpgradeProposal for IBC v3 #143).
• PromoteToPrivilegedContract (Done in Add promote / demote contract to privileged gov proposal #188).
• DemotePrivilegedContract (Done in Add promote / demote contract to privileged gov proposal #188).
• InstantiateContract. (Not needed, as contract instantiation can be done without governance.)
• MigrateContract. (Redundant. Already implemente through WasmMsg)
• SetContractAdmin (Done in Add promote / demote contract to privileged gov proposal #188).
• ClearContractAdmin (Done in Add promote / demote contract to privileged gov proposal #188).

These should be implemented as part of tgrade-validator-voting.