Convert npm version-level package.json as metadata partially

[yma955]

Now considered npm version-level package.json is a sort of special metadata in Charon. It's partially generated from Charon, and most fields are coming from uploading. We still need to keep its .prodinfo to make it able to roll back thoroughly, so manifest will keep it as well.

[coveralls]

Pull Request Test Coverage Report for Build 2146224160

• 11 of 14 (78.57%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 78.66%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
charon/storage.py	5	8	62.5%

Totals
Change from base Build 2100968136:	0.3%
Covered Lines:	1515
Relevant Lines:	1926

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💛 - Coveralls

[ligangty]

LGTM