More tests for lens

[roman-khimov]

Is your feature request related to a problem? Please describe.

I'm always frustrated when we don't have enough tests for recovery/maintenance tools we provide. We've got lens, but it's almost untested.

Describe the solution you'd like

Cover fstree, meta and storage sections of lens. Add more tests for resync (with broken data, inconsistencies (lock/tomb), etc).

Additional context

nspcc-dev/neofs-node#3824
nspcc-dev/neofs-node#3823
nspcc-dev/neofs-node#3827
nspcc-dev/neofs-node#3826
nspcc-dev/neofs-node#3825

[evgeniiz321]

@roman-khimov can you please add more details for test scenarios for the meta resync? e.g. with broken data, inconsistencies (lock/tomb) - i need more information on what exactly we want to check.

[roman-khimov]

Broken data: shred a file in fstree, empty it, rename to lalala.
Inconsistencies: form a lock and a tomb for the same object, put them into fstree, resync.