ci: codecov: use gcovr and upload cobertura style file

Use gcovr to generate reports and upload cobertura style file instead of
previously lcov info file.

We have been seeing issues with lcov format and code being reporting as
not covered although by inspecting the generate output files, they
should be.

The XML format we generate is otherwise easier to parse and deal with.

Also reduce frequency to twice a day.

Fixes #66656

Signed-off-by: Anas Nashif <anas.nashif@intel.com>