Codecov indicates coverage change when no source code is touched

## Required information

**Operating system:**
All compilers

**Compiler version:**
All compilers

**Observed result or behaviour:**
When Pull-Request are opened, the codecov still post a comment in the PR that the coverage was touched even when no codefiles are modified.
Example: https://github.com/eclipse-iceoryx/iceoryx/pull/773/files

It seems that often the coverage involving smart_c.inl is flickering. The timing_tests are already uploaded in a separate codecov target but there are still flacky tests. It could be also a wrong configuration in codecov.

- [ ] Update Codecov Uploader in Github CI to V2 https://about.codecov.io/blog/codecov-uploader-deprecation-plan/ and https://github.com/marketplace/actions/codecov#%EF%B8%8F--deprecration-of-v1
- [ ] Ensure that there are no flacky tests in the output of gcov/lcov
- [ ] Investigate a possible misconfiguration in the codecov configuration

**Expected result or behaviour:**
Code Coverage should only change when test files are modified.

**Conditions where it occurred / Performed steps:**
Open a Pull-Request without modifying source code files.