docs: Move the python libraries to tools/lib/python

"scripts/lib" was always a bit of an awkward place for Python modules.  We
already have tools/lib; create a tools/lib/python, move the libraries
there, and update the users accordingly.

While at it, move the contents of tools/docs/lib.  Rather than make another
directory, just put these documentation-oriented modules under "kdoc".

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20251110220430.726665-2-corbet@lwn.net>

tools/docs/check-variable-fonts.py

@@ -9,13 +9,17 @@
 """
 Detect problematic Noto CJK variable fonts.
 
-or more details, see lib/latex_fonts.py.
+or more details, see .../tools/lib/python/kdoc/latex_fonts.py.
 """
 
 import argparse
 import sys
+import os.path
 
-from lib.latex_fonts import LatexFontChecker
+src_dir = os.path.dirname(os.path.realpath(__file__))
+sys.path.insert(0, os.path.join(src_dir, '../lib/python/kdoc'))
+
+from latex_fonts import LatexFontChecker
 
 checker = LatexFontChecker()