allow programmatic updates of artifact description, metadata, aliases

[coveralls]

Pull Request Test Coverage Report for Build 5abe3d2d-465c-4b5b-8fcd-c62f2cb999d0

• 11 of 21 (52.38%) changed or added relevant lines in 2 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.004%) to 60.992%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
wandb/apis/public.py	9	19	47.37%
<!--	Total:	11	21	52.38%	-->

Files with Coverage Reduction	New Missed Lines	%
wandb/compat/tempfile.py	2	59.09%
<!--	Total:	2		-->

Totals
Change from base Build cedef85c-1646-468e-a0c4-2320930b9d24:	-0.004%
Covered Lines:	12920
Relevant Lines:	21183

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💛 - Coveralls