PR to close #38

[muehlke]

This PR is aimed at fixing the FC timeout error test case so that it checks this error on both tp implementations (ISOTP_C and ISOTP_SOCK).

Tested locally on a Ubuntu machine (24.04.1 LTS, x86_64) with bazel test //test:all and all tests passed, just testing the fuzz server was skipped.

[driftregion]

This is a wonderful proof of concept but the implementation is too complex, mostly due to the existing implementation of env.c that you have successfully worked around.

• Could the test function void TestISOTPFlowControlFrameTimeout(...) be made simpler by making separate test function for each tp type?
• Consider using a custom setup function that does not register a server tp rather than conditionally calling ENV_TpFree(srv); in the test. Note that unique setup and teardown functions may be passed to cmocka_unit_test_setup_teardown.
• Ideally, ENV_RunMillis runs everything registered and there is no need to run a specific transport.