Make AzDO builds use artifacts dir laid out the same as local build's artifacts dir

[dagood]

To make it easier to understand and reproduce the build, the AzDO builds (CI, official build, etc.) should probably be laid out the same as a local build.

artifacts/transport/coreclr/... => artifacts/...
artifacts/transport/librariesallconfigurations => artifacts/... (pending #1016)

A main difficulty is that these artifacts may overlap. In AzDO, overlap causes failures. In a local build, overlap is handled by the last write winning. Any overlap seems undesirable (can we be sure it's happening intentionally?) so I think we should try to prevent that before going forward with artifacts dir consolidation.

(Brought up in #1016 (comment))