Minor code improvements
- Remove / add empty lines
- fix the `ttcapture` comment
- remove the `bonus` variable for `ttMoveHistory`
- remove unnecessary parentheses / brackets
- refactor the movepick good quiet stage
- rename `endMoves` to `endCur`, as the previous name suggests that it points to the end of all generated moves, which it does not.
closes https://github.com/official-stockfish/Stockfish/pull/6089
No functional change.
Co-Authored-By: xu-shawn <50402888+xu-shawn@users.noreply.github.com>