Fix final PV output when Skill Level is enabled
If Skill Level is enabled, master may not always show the correct final PV (and eval) corresponding to the chosen bestmove. This PR fixes this by setting `uciPvSent` to false if a swap of rootmoves took place.
Example:
```
setoption name Skill Level value 0
go depth 10
```
Master:
```
info depth 10 seldepth 11 multipv 1 score cp 23 nodes 13995 nps 424090 hashfull 2 tbhits 0 time 33 pv e2e4 e7e5 g1f3 b8c6 d2d4 e5d4 f3d4
bestmove d2d3 ponder d7d5
```
Patch:
```
info depth 10 seldepth 11 multipv 1 score cp 23 nodes 13995 nps 311000 hashfull 2 tbhits 0 time 45 pv e2e4 e7e5 g1f3 b8c6 d2d4 e5d4 f3d4
info depth 10 seldepth 10 multipv 1 score cp 18 nodes 13995 nps 311000 hashfull 2 tbhits 0 time 45 pv d2d4 g8f6 g1f3 d7d5 c2c4 c7c6 e2e3
bestmove d2d4 ponder g8f6
```
closes https://github.com/official-stockfish/Stockfish/pull/7267
No functional change