Network-accessing classes need to be testable

[andrewazores]

Currently there are several classes which create TCP sockets or HTTP client connections (some examples: RecordingExporter, UploadSavedRecordingsCommand, SocketClientReaderWriter, SocketInteractiveShellExecutor, JMCConnection), and which are partly or entirely missing unit tests since the networking codepaths can not be exercised in unit testing without actually producing network connections. We need some enhanced mocking utilities, or a test harness to intercept connections, in order to properly test and verify these classes.

[andrewazores]

JMCConnection has been moved to https://github.com/rh-jmc-team/container-jfr-core

[andrewazores]

This is improved since #23 since fewer classes directly establish connections, but NetworkResolver, RecordingExporter, and SocketClientReaderWriter need testing. Particularly the latter two as they are larger and relatively complex.