Add coverage baseline support for the full option

[o-mago]

I think the coverage baseline was planned to work with the full mode:
https://github.com/Azure/gocover/blob/main/pkg/gocover/options.go#L30C35-L30C35

So, it would be nice to make it easier integrate with github actions if it had this option for full mode:
./gocover full --cover-profile=coverage.out --excludes='**/*_mock.gen.go/**' --coverage-baseline=80