Respect default *print-length* and *print-level* in debugger output

[yuhan0]

Fixes clojure-emacs/cider#2621

I'm not familiar at all with the internals of cider-nrepl, but having been annoyed by the above issue one too many times I decided to grep for *print-length* in this repo and found that simply changing these lines solved the issue.

Perhaps there's a better way to tackle it, hopefully this PR gives a starting point :)

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

• The commits are consistent with our contribution guidelines
• 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]

We should track down why the print-options are nil in the debugger, as I'm pretty sure something's set by default in CIDER (and they were supposed to fallback to *print-length* and friends anyways). Mostly likely something is not passed/set properly somewhere. Btw, the print options come straight from nREPL - they are not something specific to cider-nrepl.

[bbatsov]

I'm wondering why print-options is some var, as if I recall correctly it's passed as part of each nREPL message. Most likely it's not initialized properly. Perhaps we broke something when we introduced support for nREPL 0.6.

[bbatsov]

Just as I figured the problem is that what we current sent to init the debugger is not what the debugger expects:

(-->
  id                             "7"
  op                             "init-debugger"
  session                        "da8bc456-b029-4d88-b295-3fe4189f2a3c"
  time-stamp                     "2019-10-03 09:16:08.460679000"
  nrepl.middleware.print/options (dict
                                   right-margin 80)
  nrepl.middleware.print/print   "cider.nrepl.pprint/pprint"
  nrepl.middleware.print/quota   1048576
  nrepl.middleware.print/stream? "1"
)

On the other hand the debugger does the initialization like this:

(defn- initialize
  "Initialize the channel used for debug-input requests."
  [{:keys [print-options] :as msg}]
  (when (map? @debugger-message)
    (debugger-send :status :done))
  ;; The above is just bureaucracy. The below is important.
  (reset! @#'print-options print-options)
  (reset! debugger-message msg))

But there's no key named print-options and that's the real problem. That will be a simple fix, but probably your suggestions also makes sense in the absence of some explicit print options.