ENH: initialize a few more MinimizerResult attributes

[reneeotten]

Description

This PR initializes a few more attributes of the MinimizerResult class, as discussed on the mailinglist.

Type of Changes

• Bug fix
• New feature
• Refactoring / maintenance
• Documentation / examples

Tested on

Python: 3.9.9 (main, Nov 16 2021, 07:21:43)
[Clang 11.0.3 (clang-1103.0.32.62)]

lmfit: 1.0.3.post10+ga7298d4, scipy: 1.7.3, numpy: 1.21.4, asteval: 0.9.25, uncertainties: 3.1.6

Verification

Have you

• referenced existing Issue and/or provided relevant link to mailing list?
• verified that existing tests pass locally?
• verified that the documentation builds locally?
• squashed/minimized your commits and written descriptive commit messages?

[codecov]

Codecov Report

Merging #771 (d27a5aa) into master (275d830) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head d27a5aa differs from pull request most recent head 8464709. Consider uploading reports for the commit 8464709 to get more accurate results

@@           Coverage Diff           @@
##           master     #771   +/-   ##
=======================================
  Coverage   93.75%   93.75%           
=======================================
  Files          10       10           
  Lines        3411     3413    +2     
=======================================
+ Hits         3198     3200    +2     
  Misses        213      213           

Impacted Files	Coverage Δ
lmfit/minimizer.py	90.80% <100.00%> (+0.02%)	⬆️

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[newville]

@reneeotten Thanks - happy to merge this when you say it is ready.