Add support for configuring various sync timeouts.

The Swift API is here: https://www.mongodb.com/docs/realm-sdks/objc/latest/Classes/RLMSyncTimeoutOptions.html, but the Kotlin API might look slightly different as we haven't really supported nested configuration objects until now.

One suggestion might be to have nested builders, which create an DSL, something like:

```
val appConfig = AppConfiguration.Builder("appId")
.syncTimeOuts

{ // this: SyncTimeoutsBuilder pingKeepalivePeriod = 10.seconds }

.build()
```