Fix code smells

[abitmore]

• Add GCOVR_EXCL_LINE markers to some FC_CAPTURE_* lines so that the code coverage reports make more sense. Note: the GCOVR_EXCL_BR_LINE marker would make even more sense for us, but it's added in gcovr version 6.0, in our main CI environment (Ubuntu 20.04 LTS) the version of gcovr is 4.2 (see https://gcovr.com/en/6.0/guide/exclusion-markers.html and https://gcovr.com/en/5.2/guide/exclusion-markers.html).
• Make some unused function parameters unnamed, and add tests.
• Fix other code smells

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

88.0% Coverage
0.0% Duplication