Add support for using Azure Dev Ops pipeline caching

[christiango]

Azure Devops has added the pipeline caching feature which enables sharing the output of a previous build to speed up the outputs of the next build. This has a dedicated Azure Devops task and handles some security/compliance concerns necessary for using backfill in the Office 365 engineering system.

It would be great to see what overlap there is between backfill and ADO pipeline caching and adding first class support for using pipeline caching as a storage location for backfill

[bweggersen]

We just discussed this topic again. Let's look into creating a new Storage Provider that uses ADO Pipeline Caching APIs, if we can get access those.