USA and International road shield support & polish

[nvkelso]

Back in 2017 we started adding new artwork and logic for USA and international roads shields in #262. That work needs to be finished, including the following shield polish improvements:

• Some text colors need to change from black to say green or blue or reverse (see Australia)
• Some text needs to be offset (usually up/down) inside the shield art (see Nevada, Washington state)
• Some shield textures coordinates are corrupted leading to confetti artwork (usually because of a negative x, y value on edge of spritesheet)

See also:

• https://docs.google.com/document/d/1gs-iO_oi3Kt-_7s6wwm2Ca-HyKLvokSEM_06bBJfYhI/edit