Identify and resolve CircleCI cache key conflicts

[jrgriffiniii]

As discovered within https://github.com/samvera/browse-everything/pull/403/files#r898011114, there seem to be cases where the Ruby and Rails versions are used to generate CircleCI cache keys which cannot readily be reused without introducing breaking changes for a given branch.

[cjcolvar]

When looking into this yesterday I had the thought of dropping the bundle command in favor of the official ruby orb's command, but it looks like it might have the same sort of problem. It might still be worth considering using it anyways to avoid having to maintain the command ourselves.
https://github.com/CircleCI-Public/ruby-orb/blob/365d475512a3b4eafca54ece98a878f93aa49b30/src/commands/install-deps.yml#L36