[FLINK-23296] [core] Introduce RequestReplyClientFactory extension

* Rename default HTTP request-reply client
* Implement default HTTP client factory
* Wire in RequestReplyClientFactory into HttpFunctionEndpointProvider
* Pass in ExtensionResolver when binding JsonEntities
* Bump YAML format version
* Implement v3.1 YAML format with transport spec parsing
* Implement context-safe decorator for RequestReplyClient
* Ensure correct classloader when using tranport clients and factories
* Move Classloader handling responsibility to factory implementations
* Add TransportClientsModule

This closes #243.
27 files changed