fix(cli): Configure and enable a git-annex remote when downloading datasets

[nellh]

Adds a new git-annex worker command to enable remote configuration. This will setup a working remote during download to skip the enableremote step before using datalad get or git-annex get on objects in a downloaded dataset.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 37 lines in your changes missing coverage. Please review.

Project coverage is 46.81%. Comparing base (794f576) to head (8ce2032).
Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
cli/src/worker/git.ts	0.00%	31 Missing ⚠️
cli/src/commands/download.ts	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3283      +/-   ##
==========================================
- Coverage   46.85%   46.81%   -0.04%     
==========================================
  Files         610      610              
  Lines       39102    39142      +40     
  Branches     1254     1255       +1     
==========================================
+ Hits        18321    18325       +4     
- Misses      20585    20621      +36     
  Partials      196      196              

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