refactor: adds Client/Reqeust customizer for HttpClientSseClientTransport#117

Aliaksie wants to merge 4 commits intomodelcontextprotocol:mainmodelcontextprotocol/java-sdk:mainfrom

Aliaksie:issue114/clean-httpClientSseClientTransportAliaksie/mcp-java-sdk:issue114/clean-httpClientSseClientTransportCopy head branch name to clipboard