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>

zsh-completions/_proxmox-file-restore

@@ -0,0 +1,13 @@
+#compdef _proxmox-backup-client() proxmox-backup-client
+
+function _proxmox-backup-client() {
+    local cwords line point cmd curr prev
+    cworkds=${#words[@]}
+    line=$words
+    point=${#line}
+    cmd=${words[1]}
+    curr=${words[cwords]}
+    prev=${words[cwords-1]}
+    compadd -- $(COMP_CWORD="$cwords" COMP_LINE="$line" COMP_POINT="$point" \
+        proxmox-file-restore bashcomplete "$cmd" "$curr" "$prev")
+}