Stacktrace at point or in region

[r0man]

This PR adds Stacktrace at point or in region support.

Please see: https://github.com/clojure-emacs/orchard/pull/164

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Before submitting a PR make sure the following things have been done:

• [x] The commits are consistent with our contribution guidelines
• [x] You've added tests to cover your change(s)
• [ ] All tests are passing
• [ ] The new code is not generating reflection warnings
• [ ] You've updated the README (if adding/changing middleware)

[bbatsov]

Looks good, failing CI aside.

[r0man]

@bbatsov @vemv This one would be ready from my side.

[bbatsov]

After merging it I noticed we forgot to update the changelog.

[bbatsov]

It also seems to me you've updated ops.adoc manually, instead of generating it from the middleware descriptors. This will have to be fixed, otherwise your nice docs will disappear once this is regenerated with the lein docs task.

[r0man]

Oops, I opened another PR to address those issues: https://github.com/clojure-emacs/cider-nrepl/pull/762