Refinements for alternative clients

[shawkins]

Is your task related to a problem? Please describe

There are some adjustments needed to the api and usage model.

Describe the solution you'd like

• The ssl configuration should provide the key and trust managers rather than the context.
• The WatchHTTPManager should use a different thread to handle the InputStream. Using the thread that calls whenComplete on the returned future is only safe for okhttp.
• A refinement should be made to interceptors to make non-blocking calls - token refreshes are current blocking

Some additional one-off threads being created by the client:

• ExecWebSocketListener, LogWatchCallback, and PodUpload for inputstream pumping - these are candidates for refactoring, but require new/different surrounding apis to fully take advantage of new calling styles. PodUpload is already due to be reworked by Remove PodUploadWebSocketListener #3856
• PortForwarderWebsocket to start a listener thread
• A shared scheduling thread in Utils

Describe alternatives you've considered

No response

Additional context

No response

[shawkins]

It is not strictly required that responses return strings. Deserialization already accepts inputstream. The only place a string return value is used is with reading logs.