Add Function to Enable Application Layer to Send Direct Control Messages

Nobody has claimed this yet.

### Description

**Proposal**: Introduce a new function, `SendControl`, to the `GossipSubRouter` that allows the application layer to send direct control messages to a peer. This feature will primarily be used to develop finer-grained testing. [Flow blockchain](https://github.com/onflow/flow-go/blob/master/insecure/corruptlibp2p/gossipsub_spammer.go#L69-L73) currently uses this feature quite extensively.

### Proposed Function

```go
// SendControl dispatches the given set of control messages to the given peer.
func (gs *GossipSubRouter) SendControl(p peer.ID, ctl *pb.ControlMessage, msgs ...*pb.Message) bool {
out := rpcWithControl(msgs, ctl.Ihave, ctl.Iwant, ctl.Graft, ctl.Prune)
return gs.sendRPC(p, out)
}
```

Sample implementation on my [forked](https://github.com/yhassanzadeh13/go-libp2p-pubsub/blob/master/gossipsub.go#L1930-L1934) version.

### Rationale
Adding this function does not break encapsulation drastically. It is available at the router-level, meaning it is only accessible if the application layer [creates a router and passes it to a pubsub](https://github.com/yhassanzadeh13/go-libp2p-pubsub/blob/master/gossipsub.go#L215-L217) instance, rather than creating a [gossipsub](https://github.com/yhassanzadeh13/go-libp2p-pubsub/blob/master/gossipsub.go#L208-L212) instance directly. This ensures controlled usage and maintains the integrity of the encapsulation.

### Benefits
- Enables finer-grained testing.
- Provides more control for application layer developers.
- Maintains encapsulation integrity by limiting accessibility.

I can make the PR upon a soft approval.

Start in gossipsub.go at GossipSubRouter and review the proposed SendControl entry point, along with rpcWithControl and sendRPC. Compare the linked fork implementation and identify the relevant existing tests or control-message paths; done means the router can dispatch the supplied control messages directly to the requested peer.

Written by the indexing model from the issue text.