Refactor using CWarning.with_warn #215

Tracking this Coq PR rocq-prover/rocq#13776

when this PR is merged, you should be able to rely on the new CWarnings.with_warn function instead of the ad hoc code for doing the same thing at

QuickChick/plugin/quickChick.mlg

Lines 147 to 151 in 56452d2

	let warnings = CWarnings.get_flags () in
	let mute_extraction = warnings ^ (if warnings = "" then "" else ",") ^ "-extraction-opaque-accessed" in
	CWarnings.set_flags mute_extraction;
	Flags.silently (Extraction_plugin.Extract_env.full_extraction (Some mlf)) [qualid_of_ident main];
	CWarnings.set_flags warnings;

.