Add extra dependencies for coverage testing

[kwabenantim]

Summary

Add libcpanel-json-xs-perl in custom images to help speed up parsing coverage data.

Supports Chaste/Chaste#623

[fcooper8472]

@kwabenantim just flagging that this made a massive difference: 16m down to 1m21s. (And the other changes on that PR bring it down from 34m). Definitely worth adding.

[fcooper8472]

@kwabenantim can this easily get built into -tip now?

[kwabenantim]

@kwabenantim can this easily get built into -tip now?

@fcooper8472: I've now updated -tip. It has the same dependency versions as before, plus the new libcpanel-json-xs-perl dependency.

docker pull chaste/runner:portability-dev
docker tag chaste/runner:portability-dev chaste/runner:portability-tip
docker push chaste/runner:portability-tip