Let's fix the tests enough to run with AddressSanitizer and UB Sanitizer and enable those in CI

[anordal]

This PR adds an option to build with sanitizers, fixes all AddressSanitizer and UB-Sanitizer errors (because these sanitizers can be run together) and enforces them in CI.

Motivation: The tests were crashing when compiled with Gcc 13. With these fixes, they no longer do.

I think it would be nice for future development to run the tests with sanitizers in CI to prevent the sort of bugs I've now fixed. They were not few, which should contribute to reduce the amount of flakiness (especially crashiness) in the tests.

I have focused on what's necessary to enable these sanitizers, but there is more. Particularly uninitialized variables. The next I would do is ban it with -Werror=maybe-uninitialized, but that's going to reveal the rest of that iceberg.

Test Matrix

• Tests shall now pass both with cmake -DSANITIZE=address,undefined and cmake -DSANITIZE=.
• Tests shall now pass both for Gcc 11 and 13 (and hopefully 12).
• Code coverage shall be perfect on all metrics (line, function, branch) when compiling with no sanitizers (regardless of compiler). Fixing line coverage with sanitizers is still more work, but branch coverage is currently not attainable (presumably due to artificial branches that get inserted but not ignored).

Checklist:

• [x] I have tested my changes. No regression in existing tests.
• [x] Code coverage: There are no changes in this PR that don't already have 100% branch coverage by unit-tests.

Related Issue

None.

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[tony-josi-aws]

@anordal Thanks for taking time to contribute to FreeRTOS+TCP. Enabling address and undefined behavior sanitizers in the CI check would help improve the code quality.

[tony-josi-aws]

@anordal can you help fix the merge conflict with the test/unit-test/FreeRTOS_TCP_IP/FreeRTOS_TCP_IP_utest.c?

[anordal]

Yes. I see you fixed a use after free (ba6ba81f). I'll push a rebase.