We should migrate from packaging and deploying the Chrome executables in Fuchsia from BootFS to PackageFS/Blobstore.

We've been bitten by some limitations with BootFS, namely the restriction against cloning FDs for files residing inside a BootFS volume.

Once that change is made, we should modify ChildProcessLauncherHelper to read files directly from the BootFS volume rather than make copies in tmpfs.