Cleanup: Create custom method unsupported errors

## Describe the proposal
Today we find multiple instances of these in our codebase:
```ts
async subscribe(_storeName: string, _cb: SubscribeConfigurationCallback): Promise {
throw new Error('HTTP is currently not supported.');
}

getRegisteredActors(): Promise {
throw new Error('GRPC is currently not supported.');
}
```

This proposal is to create two custom Errors: `HttpNotSupportedError` and `GrpcNotSupportedError` which can be reused in our code.