This commit adds detection of ambiguous ``std:label`` and ``std:term`` references (due to case-insensitivity)
during loading and resolution of Intersphinx targets,
and emits a warning if found.
Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>
Co-authored-by: Chris Sewell <chrisj_sewell@hotmail.com>