Fix #7319 Introduce 'du' command inside restore menu

Fix #7319 Introduce 'du' command inside restore menu

Description:
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Restore menu's du commands mimics Linux 'du' commands in terms that it
simply sums size of all files in directories below. For files, it simply
prints it's sizes.

TREE_NODE`s delta_seq size was reduced to int16_t since we don't expect
it to be any bigger at all while it reduced struct`s size a little bit
(it was still expanded by the `size` filed though).