Add support for publishing of blobs to dotnetcli(checksums) storage

[riarenas]

We don't have a great story using stages for blobs that need to be published to a final location (commonly the dotnetcli storage account)

Today, the pattern would be to implement a new stage that does the required steps, but we should find where the gaps are and see what makes sense to provide out of the box.

core-setup, core-sdk, and AspNetCore come to mind

CC @dagood, @livarcocc, @dougbu

[riarenas]

When working in the toolset repo, I was able to follow the pattern of:

• Publish all blobs to build artifacts
• Publish all blobs from build artifacts to a feed.

This worked well in toolset's case because they publish their blobs to the same feed as their packages. I'm working on allowing passing the credentials for the blob publish separately, so that it's possible to publish them to a different storage account.

[riarenas]

#3697 adds a new publishInstallersAndChecksums parameter to the post-build yaml template. When set, the parameter will publish all installers and checksums in the asset manifests to the dotnetcli and dotnetclichecksums storage accounts.

Will keep the issue in validate, and will add the parameter to my current doc updates.