Remove the LockingFileSystem and LockingRawFileSystem types from the
public API.

This reduces API clutter.
Hide bufferpool implementations to reduce API clutter.
Hide Debug public members behind SetDebug method.
fuse/test: update for Debug convention
fuse: Hide the RawFileSystem implementation of FileSystemConnector behind
the RawFS() method.
Add new packages to all.bash.
fuse: remove HandleMap and Handled from the API.
Hide PrefixFileSystem type.
Hide LoopBackFileSystem type to reduce API clutter.
Hide ReadOnlyFileSystem type to reduce API clutter.