Simplify "easy move" detection

Detect a move as easy only if it is the only one ;-)
or if is much better than remaining ones after we
have spent 20% of search time.

Tests are ongoing, but it seems this semplification
stands. Anyhow it is experimental for now and could
be reverted/improved with further work Gary is
testing right now.

No functional change.
Revert "Store moves sent with "position" UCI command"

This reverts commit 0d68b523a390e2f5c37f211316869d798e852289.

After easy move semplification this machinery is not
needed anymore (because of we don't need to know if a
root move is a recapture)

No functional change.
Increase see prune depth

This seems good at short TC controls.

After 10000 games at 20+0.05
ELO: 9.56 +-6.8 (95%) LOS: 100.0%
Total: 10000 W: 1949 L: 1674 D: 6377

Testing at long TC and regression testing is still
ongoing. So this is a bit speculative commit and
could be reverted in the future.

Also re-testing at long TC the SEE pruning in PV nodes
seems less effective (perhaps even a regression, but
still ongoing) so disabled for now.

bench: 4968764