Store remote metadata in the on disk action cache #8248
Description
This is part of #6862.
The persistent action cache stores the state of Bazel's output base. It does not know about remotely stored files. We need to extend it to do so.
$ bazel build :foo --experimental_remote_download_outputs=minimal
$ bazel shutdown
# This will be clean build, because the metadata from the previous build are
# not yet properly persisted to disk
$ bazel build :foo --experimental_remote_download_outputs=minimal