PSA: composite device topological paths are changing

[Tamir Duberstein]

As a historical accident, composite devices' topological paths have been rooted at the top level e.g. "/dev/aml-secure-mem/aml-securemem".

This turns out to produce path collisions in /dev/, which were also permitted as a historical accident.

We are landing https://fuchsia-review.googlesource.com/c/fuchsia/+/732867 which changes composite devices' topological paths to be rooted at their primary parent; the example above changes to "/dev/sys/platform/05:03:1a/aml-secure-mem/aml-securemem".

We are also landing https://fuchsia-review.googlesource.com/c/fuchsia/+/736747 which turns duplicate topological paths into hard errors, which will prevent regressions.

Please see the release notes on both CLs for further details and reach out if you are impacted.