Generate code coverage HTML pages on master builds

Right now, we are generating only XML code coverage (and numbers) that are used on MR to identify new untested code.

It would be great to have the HTML coverage reports generated in HTML from master builds too and pushed to gitlab pages, similarly as we have done in libcacard:

https://gitlab.freedesktop.org/spice/libcacard

After clicking on coverage badge, it lands on the HTML coverage report, which might be a good start for looking for untested code and easier than building coverage reports locally.