Use cli instead of crayon for console output

[olivroy]

Branched out from #589

The visual change is the following:

Current CRAN:

This PR:

Since covr doesn't import rlang, we can't use cli::cli_inform(), so I am using cli::format_message() + message() instead

[jimhester]

Can you please add a bullet to NEWS? It should briefly describe the change and end with (@yourname, #issuenumber).

[jimhester]

Thanks!