feat: improve template coverage cfg

[jennifer-richards]

Allows full file path exclusions, not just filename-only globs

>>> from ietf.utils.test_runner import *
>>> old_templates = old_get_template_paths()  # removed, just for reference
>>> new_templates = set(get_template_paths())
>>> old_templates - new_templates
set()

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ?

Project coverage is 88.74%. Comparing base (f380b1a) to head (af8eb20).
Report is 21 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9230      +/-   ##
==========================================
- Coverage   88.74%   88.74%   -0.01%     
==========================================
  Files         321      320       -1     
  Lines       41853    41652     -201     
==========================================
- Hits        37144    36965     -179     
+ Misses       4709     4687      -22     

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