Field image JSON support

[calcmogul]

We'll likely need this in 2027 when we support both FRC and FTC.

Here's the existing JSONs:
https://github.com/wpilibsuite/allwpilib/tree/main/fieldImages/src/main/native/resources/edu/wpi/first/fields

[shueja]

d9b23ee

The commit that removed when I did this before as a helper for verifying the SVG field elements.

This isn't a full implementation of the feature request but it's most of the tricky positioning/scaling code.

Outside of just changing the background image, there's questions about how the field dimensions should be used. Until 2027 (field center origin), any alliance-based sample flipping needs the field dimensions, so as a separate but related feature, dimensions should be settable configs in ChoreoLib or be part of the exported trajectory.