Steps/checks should be able to signal medic to reload its environment

[sax]

When run with --interactive or --apply-remedies, medic may make changes to the system that are reflected in changes to environment variables such as PATH; this is easily replicable when using medic-ext-tool-versions with mise, when a new version must be installed.

Future steps may do the wrong thing, because medic has not reset its environment.

[sax]

Maybe after running a remedy, medic should always reload its environment.