feat(artifacts): Add support for IAM roles for service accounts in artifact storage. Fixes #1774

[dcherman]

Fixes #1774

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234". Why? for the release notes.
• Optional. I've added My organization is added to the README.
• I've signed the CLA and required builds are green.

[alexec]

Approval. Can merged with green builds.

[codecov]

Codecov Report

Merging #1899 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1899   +/-   ##
=======================================
  Coverage   11.14%   11.14%           
=======================================
  Files          35       35           
  Lines       23536    23536           
=======================================
  Hits         2624     2624           
  Misses      20576    20576           
  Partials      336      336

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