logging: Ensure -debug=0/none behaves consistently with -nodebug

Previously, -nodebug cleared all prior -debug configurations in the
command line while allowing subsequent debug options to be applied.
However, -debug=0 and -debug=none completely disabled debugging,
even for categories specified afterward.

This commit ensures consistency by making -debug=0 and -debug=none
behave like -nodebug: they now clear previously set debug configurations
but do not disable debugging for categories specified later.

Co-Authored-By: Ryan Ofsky <ryan@ofsky.org>

doc/release-notes-31767.md

@@ -0,0 +1,3 @@
+Logging
+---
+Passing -debug=0 or -debug=none now behaves like -nodebug: previously set debug categories will be cleared, but subsequent -debug options will still be applied.