Extract repr_html directly from cube summary

[stephenworsley]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 92.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.83%. Comparing base (92e1e96) to head (c2e1764).
⚠️ Report is 136 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/iris/experimental/representation.py	92.50%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6476      +/-   ##
==========================================
- Coverage   89.83%   89.83%   -0.01%     
==========================================
  Files          90       90              
  Lines       23828    23820       -8     
  Branches     4448     4452       +4     
==========================================
- Hits        21407    21399       -8     
  Misses       1670     1670              
  Partials      751      751              

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[ESadek-MO]

Thanks @stephenworsley, mostly looks good, thanks!

Apart from the review comments, please also add a whatsnew, then should be good to go!

[ESadek-MO]

Thanks @stephenworsley, LGTM!