Deprecate sum_expand and hamiltonian_expand

[Shiro-Raven]

[sc-64018]

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.65%. Comparing base (fdf74de) to head (ef5234e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6003      +/-   ##
==========================================
- Coverage   99.66%   99.65%   -0.01%     
==========================================
  Files         427      427              
  Lines       41040    40748     -292     
==========================================
- Hits        40902    40609     -293     
- Misses        138      139       +1     

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[PietropaoloFrisoni]

Thanks!