Run code coverage on more devices/presets

[aloisklink]

This PR changes the CI code to automatically calculate code coverage on all tested code.

Then, another CI job is run to combine the code coverage for the multiple presets into a single coverage file, which is then uploaded.

This means that if we do start testing OpenWRT code in GitHub actions, it will be automatically uploaded too.

It's also faster, since instead of having to build once for tests, and once for coverage, we can do both in one step.

Currently a draft, since this PR depends on #226

[codecov]

Codecov Report

Merging #229 (5e52e52) into main (a231aee) will increase coverage by 0.56%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #229      +/-   ##
==========================================
+ Coverage   43.67%   44.24%   +0.56%     
==========================================
  Files         100      100              
  Lines       13178    13178              
==========================================
+ Hits         5756     5831      +75     
+ Misses       7422     7347      -75     

Impacted Files	Coverage Δ
src/utils/os.c	39.35% <0.00%> (+0.64%)	⬆️
tests/capture/test_capture_service.c	70.76% <0.00%> (+3.07%)	⬆️
src/capture/middlewares_list.h	32.00% <0.00%> (+12.00%)	⬆️
.../middlewares/header_middleware/header_middleware.c	17.56% <0.00%> (+17.56%)	⬆️
...iddlewares/cleaner_middleware/cleaner_middleware.c	18.34% <0.00%> (+18.34%)	⬆️
...ture/middlewares/pcap_middleware/pcap_middleware.c	26.44% <0.00%> (+26.44%)	⬆️

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[mereacre]

Great