feat: market: Add lotus-shed cmd to get total active deal storage

[shrenujbansal]

Related Issues

#9083

Proposed Changes

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• The PR title is in the form of of <PR type>: <area>: <change being made>
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[arajasek]

Looks good, and tested it out -- it works! Thanks for this!

Feel free to land after addressing @geoff-vball 's two suggestions.