feat(group): Prune expired proposals and votes (#11315)

## Description

Closes: #11245

### 1. Pruning proposal.

Proposals are pruned:
- after a successful MsgExec (or try_exec)
- on voting_period_end + max_execution_period

whichever happens first.

### 2. Pruning votes.

Votes are pruned:
  - on MsgExec (or try_exec) if tally is final
  - on voting_period_end

whichever happens first. 

### 3. Various group fixes

See #11404 for details

TODO:
- [x] Add vote pruning after Tally, once #11310  is merged
- [x] Add tests



---

### Author Checklist

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- [ ] added a changelog entry to `CHANGELOG.md`
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Author: amaury1093

api/cosmos/group/v1/events.pulsar.go

@@ -3,6 +3,7 @@ syntax = "proto3";
 package cosmos.group.v1;
 
 import "cosmos_proto/cosmos.proto";
+import "cosmos/group/v1/types.proto";
 
 option go_package = "github.com/cosmos/cosmos-sdk/x/group";
 
@@ -60,6 +61,9 @@ message EventExec {
 
   // proposal_id is the unique ID of the proposal.
   uint64 proposal_id = 1;
+
+  // result is the proposal execution result.
+  ProposalExecutorResult result = 2;
 }
 
 // EventLeaveGroup is an event emitted when group member leaves the group.