Move cellxgene-data-public to a separate AWS account

[ebezzi]

The trust review requested that we move the existing public bucket to a separate AWS account to limit the interactions and increase the alertness level.

[pablo-gar]

This is an outcome of the trust review as detailed here #279

[atolopko-czi]

@ebezzi wrote a Trust Review doc to work through the remaining considerations that need guidance from Trust before we can finalize the architectural decisions.

[pablo-gar]

Completed