eslint configuration: adapt Jetpack's basic rules to match Calypso

@jsnmoon previously worked on simplifying our eslint configuration in #13184.

It would be nice to continue in that direction to bring us to a point where Jetpack's basic eslint configuration is similar to the one in Calypso:
https://github.com/Automattic/wp-calypso/blob/9000f926ccc67af288604471d2ea53c0befd54de/.eslintrc.js

This may involve relying on cascading some more things in both Jetpack and Calypso, but will have the advantage of unblocking issues like this one: p3topS-KH-p2

It's especially important with the eslint plugins in use and that will need to be available in all environments.

cc @Automattic/team-calypso for their opinion on this.