feat(UI): add external tileset sprites for sails, adjust mounted flag background tiles

[chaosvolt]

Checklist

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• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax so it can be closed automatically.
• I have committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.

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Purpose of change

Gives sails some less silly sprites and changes the background tile for vehiclepart mounted flags, as I felt the "standard red car roof" looked a bit weird on a lot of other vehicles.

Describe the solution

1. Added a UDP external tileset sprite for vehicle sails that overrides the existing one, giving it a background instead of being a sail and small mast floating on nothingness.
2. Added a sprite for large sails, taking advantage of the fact that we have a limited ability to do multi-tile sprites for tilesets so long as you respect layering priority (i.e. only extend into tiles left of the tile the sprite's on, not to the right).
3. Misc: Changed the background tile for vehicle-mounted flags from bright vehicle red to a dark neutral background color.

Describe alternatives you've considered

Overriding the sail sprite itself directly in UDP itself because it will probably take an eternity for us to other get an update sent over from the Unpacked repo.

Testing

1. Checked affected files for syntax and lint errors.
2. Load-tested in compiled test build.
3. Temporarily added in a lil pirate sloop to spawn in to test that it looks good at a glance.

Additional context

I'm too eepy to keep up the "translate the PR text into pirate-speak" gag I did last PR even though it's still very early into Talk Like A Pirate Day.

[RoyalFox2140]

Classic 4am Chaos PR