[3.9] bpo-45187: Collect test_socket tests using unittest (GH-28317) by ambv · Pull Request #28413 · python/cpython

…8317)

Previously, test classes ISOTPTest, J1939Test, BasicUDPLITETest and
UDPLITETimeoutTest were not included in the list of tests and
were not run by regrtest..
(cherry picked from commit 0361335)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>