A new RPC is introduced `_registerService` which allow clients to
register new services that are accessible from all the other clients.
Each registered endpoint is identified by 3 strings:
- `service`
a non empty string which identifies the provided service
(e.g. `HotReload`, `OpenFile`)
- `alias`
an alias for that particular endpoint used by clients to identify it
(e.g. `Flutter`, `IntelliJ`)
- `method` __generated__
the RPC method that should be invoked from a client to request it
A new _stream_ `_Service` is introduce, and two related events:
- `ServiceRegistered`
which is triggered when a new client is registered.
All the related information (`service`, `alias`, `method`) are sent.
- `ServiceUnregistered`
which is triggered when a client, which previously registered a
service, disconnects.
Just `service` and `method` are sent.
Related https://github.com/dart-lang/sdk/issues/30023R=asiva@google.com, bkonyi@google.com
Review-Url: https://codereview.chromium.org/2980733003 .
Carlo Bernaschina
df8bf384eb