Modernize RSpec configuration

[dduugg]

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This PR enables some best-practice RSpec options (for reference, see the project initializer boilerplate in rspec-core). Specifically, it:

• Enables and fixes warnings (first commit). These involved a circular require and re-defining methods without undefining them first. (The latter can seem a bit silly, but I've found to be very useful in understanding code on occasion.)
• Enables and fixes verify_partial_double (second commit). This checks that the underlying object actually defines the doubled methods. This uncovered some cruft, though I had to use the escape hatch of without_partial_double_verification around ENV code that I couldn't make immediate sense of.
• Enables and fixes disable_monkey_patching (remaining commits). This setting removes RSpec methods from the top-level scope.

[MikeMcQuaid]

Looks great, thanks again @dduugg!

[MikeMcQuaid]

Looks good, thanks @dduugg! Remaining feedback can be addressed in follow-up PR, let's get this merged before it conflicts.

[MikeMcQuaid]

@dduugg Looks like some legit test failures post-rebase, sorry!

[reitermarkus]

@dduugg, can you move your last commit to a separate PR? I couldn't really finish reviewing because the “Files changed” tab just hangs.

per above, "let's get this merged before it conflicts."

[reitermarkus]

let's get this merged before it conflicts.

Merging this quickly is not a good reason to dismiss my request for being able to fully review this. I certainly can't review it any better now that it is merged.

Remaining feedback can be addressed in follow-up PR

I mean it's generally fine to make further changes to a future PR, but I was not even able to review this fully in order to provide this “remaining feedback”.

[MikeMcQuaid]

Merging this quickly is not a good reason to dismiss my request for being able to fully review this.

You did provide a round of review here and your comments were addressed.

I certainly can't review it any better now that it is merged.

You can definitely review PRs post-merge, I do this all the time. If there's problems: they can be addressed in a future PR.

I mean it's generally fine to make further changes to a future PR, but I was not even able to review this fully in order to provide this “remaining feedback”.

Another maintainer (me) was able to review it before it was merged.

[reitermarkus]

You can definitely review PRs post-merge

Sure, not if “Files changed” tab just hangs though, which is why I specifically requested to split this up.

At least the individual commits seem to work now, they were also bugged by not showing the + button for commenting last time.

[reitermarkus]

Can we unnest these instead?