Improve dumpLisp macro (#9515)

* Improve dumpLisp macro

- Remove commas from the lisp representation of the AST.
- Make the dumpLisp output "pretty" and indented.
- Improve docs of `dumpTree` and `dumpLisp` macros.

With:

    dumpLisp:
      echo "Hello, World!"

Output before this commit:

    StmtList(Command(Ident("echo"), StrLit("Hello, World!")))

Output after this commit:

    (StmtList
     (Command
      (Ident "echo")
      (StrLit "Hello, World!")))

* Re-use the traverse proc inside treeRepr for lispRepr too

- Add module-local `treeTraverse` proc.
- Also fix treeRepr/dumpTree not printing nnkCommentStmt node contents.

* More doc string updates

* Allow unindented lispRepr output for tests

* Update a test affected by the lispRepr change

* Fix dumpTree

* Add note about lispRepr and dumpLisp to changelog [ci skip]

changelog.md

@@ -38,6 +38,9 @@
 
 ### Library changes
 
+- The string output of `macros.lispRepr` proc has been tweaked
+  slightly. The `dumpLisp` macro in this module now outputs an
+  indented proper Lisp, devoid of commas.
 
 ### Language additions