* handle control protocol through websocket
The necessary behaviour is already in place,
but the wasm build only issued GETs, and the handler was not invoked.
* get DERP-over-websocket working for wasm clients
* Prepare for testing builtin websocket-over-DERP
Still needs some way to assert that clients are connected through websockets,
rather than the TCP hijacking version of DERP.
* integration tests: properly differentiate between DERP transports
* do not touch unrelated code
* linter fixes
* integration testing: unexport common implementation of derp server scenario
* fixup! integration testing: unexport common implementation of derp server scenario
* dockertestutil/logs: remove unhelpful comment
* update changelog
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Co-authored-by: Csaba Sarkadi <sarkadicsa@tutanota.de>
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