Restore IOS model filtering of "configuration last changed/NVRAM modified"

[raunz]

Pre-Request Checklist

• Passes rubocop code analysis (try rubocop --auto-correct)
• Changes are reflected in the documentation
• User-visible changes appended to CHANGELOG.md

Description

Restore IOS model filtering of "configuration last changed/NVRAM modified" in #1896, which was included in release 0.27.0, with modifications for 802.1x where configurations change without username.
Noted as remarkable change in changelog.
Closes issue #1921

[codecov-commenter]

Codecov Report

Merging #2374 (ea51374) into master (8421b2a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2374   +/-   ##
=======================================
  Coverage   62.59%   62.59%           
=======================================
  Files          30       30           
  Lines        1497     1497           
=======================================
  Hits          937      937           
  Misses        560      560           

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[ghost]

Can you please resolve the conflict? I will merge then

[raunz]

Can you please resolve the conflict? I will merge then

Resolved the changelog.