file-restore: add binary and basic commands

For now it only supports 'list' and 'extract' commands for 'pxar.didx'
files. This should be the foundation for a general file-restore
interface that is shared with block-level snapshots.

This is packaged as a seperate .deb file, since for block level restore
it will need to depend on pve-qemu-kvm, which we want to seperate from
proxmox-backup-client.

[original code for proxmox-file-restore.rs]
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

[code cleanups/clippy, use helpers::list_dir_content/ArchiveEntry, no
/block subdir for .fidx files, seperate binary and package]
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>

docs/proxmox-file-restore/description.rst

@@ -0,0 +1,3 @@
+Command line tool for restoring files and directories from PBS archives. In contrast to
+proxmox-backup-client, this supports both container/host and VM backups.
+

docs/proxmox-file-restore/man1.rst

@@ -0,0 +1,28 @@
+==========================
+proxmox-file-restore
+==========================
+
+.. include:: ../epilog.rst
+
+-----------------------------------------------------------------------
+Command line tool for restoring files and directories from PBS archives
+-----------------------------------------------------------------------
+
+:Author: |AUTHOR|
+:Version: Version |VERSION|
+:Manual section: 1
+
+
+Synopsis
+==========
+
+.. include:: synopsis.rst
+
+
+Description
+============
+
+.. include:: description.rst
+
+
+.. include:: ../pbs-copyright.rst