Do not share ssl-context between threads

This code is sharing one ssl-context object among 5 threads:

https://github.com/equinor/ert/blob/72b2ec02cd9509a3b34fd233f7e9e590b59c053c/tests/everest/test_everest_client.py#L212-L219

That might be why https://github.com/equinor/komodo-releases/actions/runs/23438918722/job/68187259282 is segfaulting

The SSL context should be thread-safe for concurrent read-only according to its documentation, but maybe we are not really using it read-only.

https://docs.python.org/3/library/ssl.html#ssl.SSLContext

Read tests/everest/test_everest_client.py around lines 212-219 and inspect how the SSL context is passed to the five threads. Compare that usage with the Python SSLContext thread-safety documentation, then verify the test no longer shares one context between threads and that the referenced CI failure is addressed.

Written by the indexing model from the issue text.