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)

---

Checklist

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

[codecov[bot]]

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 :warning:

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/duartegroup/autodE/pull/342/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=duartegroup) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/duartegroup/autodE/pull/342/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=duartegroup) | `97.38% <99.34%> (-0.02%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=duartegroup#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[shoubhikraj]

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