refactor(cli): merge doom-cli-lib into doom-cli

This was done to purge superfluous files from Doom's project structure
and simplify its entry points. And with early-init.el now acting as
Doom's universal bootstrapper (see c05e615), we don't have enough
bootstrap logic to warrant being its own file.

Also removes the redundant version check, given doom.el is assured to be
loaded before doom-cli, and performs its own check.

Ref: c05e61536e

lisp/lib/debug.el

@@ -137,10 +137,12 @@ always access it."
     ;; debugger, which would run this handler again on subsequent calls. Taken
     ;; from `ert--run-test-debugger'.
     (cl-incf num-nonmacro-input-events)
-    ;; TODO Write backtraces to file
-    ;; TODO Write backtrace to a buffer in case recursive error interupts the
-    ;;   debugger (happens more often than it should).
-    (apply #'debug args)))
+    (if (and noninteractive (fboundp 'doom-cli-debugger))
+        (apply #'doom-cli-debugger args)
+      ;; TODO Write backtraces to file
+      ;; TODO Write backtrace to a buffer in case recursive error interupts the
+      ;;   debugger (happens more often than it should).
+      (apply #'debug args))))
 
 
 ;;