Improve reporting and plotting, switch default minimizer to LMFIT, and refresh tutorials

[AndrewSazonov]

• Improves summary reporting and fit-result plotting
• Changes the default minimizer to lmfit (leastsq)
• Updates tutorials and aligns test expectations with the refactor
• Adjusts external data references after moving data from easyscience/data/diffraction to diffraction/data

[codecov]

Codecov Report

❌ Patch coverage is 85.10638% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.77%. Comparing base (883c384) to head (ec8db03).
⚠️ Report is 53 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/easydiffraction/summary/summary.py	80.76%	4 Missing and 1 partial ⚠️
.../easydiffraction/analysis/fit_helpers/reporting.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #154      +/-   ##
===========================================
+ Coverage    82.26%   88.77%   +6.51%     
===========================================
  Files           88      145      +57     
  Lines         5451     8418    +2967     
  Branches       454      854     +400     
===========================================
+ Hits          4484     7473    +2989     
+ Misses         802      675     -127     
- Partials       165      270     +105     

Flag	Coverage Δ
integration	75.13% <68.08%> (+5.18%)	⬆️
unittests	79.24% <80.85%> (+6.80%)	⬆️

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