* Move ConnectionCache back to solana-client, and duplicate ThinClient, TpuClient there
* Dedupe thin_client modules
* Dedupe tpu_client modules
* Move TpuClient to TpuConnectionCache
* Move ThinClient to TpuConnectionCache
* Move TpuConnection and quic/udp trait implementations back to solana-client
* Remove enum_dispatch from solana-tpu-client
* Move udp-client to its own crate
* Move quic-client to its own crate
* Add fallible send methods, and rpc_client helper
* Add helper to return RpcClient url
* Implement BenchTpsClient for TpuClient
* Add cli rpc and identity handling
* Handle different kinds of clients in main, use TpuClient
* Add tpu_client integration test