DHS variable step size

[shoubhikraj]

(1) Uses multiple step sizes depending on the distance thresholds
(2) Replaces only gradient based peak detection to cubic polynomial based peak detection (both energies and gradients)

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Checklist

• The changes include an associated explanation of how/why
• Test pass
• Documentation has been updated
• Changelog has been updated

[codecov]

Codecov Report

Attention: Patch coverage is 99.34211% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 97.38%. Comparing base (598b2dc) to head (5e09fa6).

Files	Patch %	Lines
autode/opt/optimisers/utils.py	98.59%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           v1.4.3     #342      +/-   ##
==========================================
- Coverage   97.40%   97.38%   -0.02%     
==========================================
  Files         200      202       +2     
  Lines       23108    23210     +102     
==========================================
+ Hits        22509    22604      +95     
- Misses        599      606       +7     

Flag	Coverage Δ
unittests	97.38% <99.34%> (-0.02%)	⬇️

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[t-young31]

LGTM – added a couple of small suggestions

[shoubhikraj]

@t-young31 Could you please check one last time before merge?

[t-young31]

awesome