[roll] Roll fuchsia [reland] Revert "[revert] Revert "[pkg-cache][pkgfs][fshost] pkg-cache provides all pkgfs directories""

This reverts commit 631fa7a0a06c38fa7e58d8398554f45ca70ea36b.

Reason for revert: All OOT clients should now handle hierarchical
rights enforcement

Original change's description:
> [revert] Revert "[pkg-cache][pkgfs][fshost] pkg-cache provides all pkgfs directories"
>
> This reverts commit 021b6cdc9d9e0bd5f91f5a083fec30e7dfd1791f.
>
> Reason for revert: Broke file access on some OOT clients.
>
> Original change's description:
> > [pkg-cache][pkgfs][fshost] pkg-cache provides all pkgfs directories
> >
> > All pkgfs directories (including pkgfs/, pkgfs/packages/,
> > pkgfs/versions/, and pkgfs/system/) are now provided by pkg-cache
> > instead of pkgfs.
> >
> > Package directories themselves (including the elements of
> > pkgfs/versions/ and pkgfs/packages/*/*/ and the /pkg directory mounted
> > in components' namespaces) are now served by pkg-cache instead of
> > pkgfs.
> >
> > The pkgfs directories and package directories themselves are
> > implemented on top of the Rust VFS library. As a result, they now
> > enforce hierarchical rights (e.g. opening a file with RIGHT_READABLE
> > requires that the directory connection over which the
> > fuchsia.io/Directory.Open FIDL call was made had RIGHT_READABLE) and
> > perform more validation of the flag, mode, and path
> > arguments (e.g. paths of the empty string and paths containing ".."
> > segments are now rejected). See
> > https://cs.opensource.google/fuchsia/fuchsia/+/main:src/sys/pkg/tests/pkgdir/README.md
> > for a full listing of the package directory behavior changes.
> >
> > fshost no longer starts pkgfs (sometimes called pkgsvr).
> >
> > pkg-cache is now routed an executable handle to blobfs (so it can serve
> > package directories).
> >
> > pkg-cache is now a child of bootstrap and is resolved by the
> > base-resolver.
> >
> > pkg-cache's other package APIs (fuchsia.pkg/PackageCache.{Open|Get}) now
> > use the same machinery that powers its pkgfs replacements (instead of
> > forwarding to pkgfs).
> >
> > Original-Bug: 99148
> > Original-Fixed: 88871
> > Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/630466
>
> Original-Bug: 99148
> Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/678298

Original-Bug: 99148
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/678507
Original-Revision: adb48d70a986bd8e1aedb084f418edd9a8653983
GitOrigin-RevId: 6785171eb8fcd5478b3328f7d4b147cdf7f7e786
Change-Id: I77e70d97f46129c4e1180eba59301ca8445e4312