Now it is enough to add:
"macros": [
"MBED_GREENTEA_TEST_XXXSOCKET_TIMEOUT_S=20"
],
to mbed_app.json, where XXX is on of {DNS, TLS, UDP, TCP}.
Also network-* tests are now configurable: network-interface, network-wifi, network-emac with a similar macro.
The whole README.md had to be updated to match the internal Confluence documentation, which can now be locked. In the process I also updated any spotted mistakes in tests documentation, removed the obsolete TCPServer tests documentation and added a test which was missing from UDPSocket's main.