feat(miniconda): --run to run arbirary commands to possibly tune up that miniconda installation

[yarikoptic]

This is at large to allow to address some issues which might come up with miniconda installations without waiting to hardcode the workarounds into datalad-installer. e.g. for

• git-annex -m conda installation fails in CI #206

with current change we can address by adding --run 'conda install libarchive --solver=classic' ATM, i.e.

src/datalad_installer.py -E /tmp/mini1.env miniconda --path /tmp/mini1 --channel conda-forge --python-match minor --batch --run 'conda install libarchive --solver=classic' git-annex -m conda

Yet to decide but if to proceed this way, need to

• add test

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 65.13%. Comparing base (d9e289a) to head (69f4fcc).

Files with missing lines	Patch %	Lines
src/datalad_installer.py	0.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #209      +/-   ##
==========================================
- Coverage   65.75%   65.13%   -0.63%     
==========================================
  Files           1        1              
  Lines        1647     1652       +5     
  Branches      284      286       +2     
==========================================
- Hits         1083     1076       -7     
- Misses        460      469       +9     
- Partials      104      107       +3     

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[yarikoptic]

for #206 decided to proceed with

• "Listen" to conda recommendation to use some other solver upon conda install failing; stderr output from "conda install" would be captured and logged #210

unless there would be a usecase for this added feature, let's just keep it in draft here for now