Tracing: Split wts tracing into trace and more verbose debug modes.

* Separator tracing is enabled only in --debug wts mode.
* This makes wts tracing more readable.
* Compare output of the two commands:

$ echo "*a\n*b\n*c" | node parse --trace wts --wt2wt
$ echo "*a\n*b\n*c" | node parse --debug wts --wt2wt

Change-Id: If79443a2f5d7010da456cf1c2717e6753a7b6b49