add Inverted Flight controls setting

• Adds per-profile option to invert vertical controls of Rockets and Rideroids: pressing down makes you go up, while pressing up makes you go down.
• Specifics of implementation: the throwdir value in a player's cmd data struct is inverted whenever the player is on a rocket/rideroid and has the inverted flight setting on.
  • This means it inverts the controls for lobbying items (as you go up or down, items will or will not be lobbied exactly as they would if you went up or down without inverted flight controls), so players with the setting enabled can't lob items in ways that players without are unable to.
  • Along with the above effect, this means that the setting doesn't take up another player flag or require additional variables in player_t.
• Replays of races with the inverted flight setting on show non-inverted up and down inputs during flying sections.
• The accessibility options menu now has one extra settings row, leaving no room for additional settings in the menu.
• Untested online.

I'm mostly creating this merge request to gauge interest on this feature, as I more or less don't think this is actually a worthwhile addition to the game: flight sections are in a grand total of 3 tracks (nearly 2% of the game's track roster!), already diminishing the importance of the feature. Furthermore, adding this would mean the last "slot" for a setting in the accessibility options menu would be occupied, and the setting would be seen early on by any player that hasn't yet unlocked the Egg Cup, much less played Lost Colony where flight mounts first appear.

if nothing else noire should be able to pick this up