Allow time checking after each DTZ probe
This PR allows for time checking within Tablebases::rank_root_moves(). The
principal application for now is syzygy_extend_pv().
In the past, Stockfish suffered some time losses at e.g. TCEC when the HDD with
the DTZ tables was too slow for the chosen move overhead setting, see #5894.
```
> ./fastchess -engine name="patch" cmd=./stockfish.patch -engine name="master" cmd=./stockfish.master -each tc=10+0.1 option.SyzygyPath=/disk1/syzygy/3-4-5-6/WDL:/disk2/syzygy/3-4-5-6/DTZ -draw movenumber=34 movecount=8 score=20 -openings file=UHO_Lichess_4852_v1.epd format=epd -rounds 50 -repeat -concurrency 16
...
Results of patch vs master (10+0.1, 1t, 16MB, UHO_Lichess_4852_v1.epd):
Elo: 59.64 +/- 35.35, nElo: 117.61 +/- 68.10
LOS: 99.96 %, DrawRatio: 56.00 %, PairsRatio: 4.50
Games: 100, Wins: 34, Losses: 17, Draws: 49, Points: 58.5 (58.50 %)
Ptnml(0-2): [0, 4, 28, 15, 3], WL/DD Ratio: 0.87
--------------------------------------------------
Player: master
Timeouts: 19
Crashed: 0
Finished match
```
closes https://github.com/official-stockfish/Stockfish/pull/6422
No functional change