New car support docs

[adeebshihadeh]

This is v2 of CARS.md. Currently, CARS.md shows all the cars supported by upstream openpilot. The goal of this new page is to be a one stop shop to see the status of any car's support.

It'll include:

• every single car: cars supported in upstream, dashcam cars in upstream, cars supported in forks (even if they're forever in forks), cars we know won't work (no ACC/LKAS), cars with blockers (SecOc), etc.
• super granular columns: has fuzzy fingerprinting, steering torque, etc.
• some info will be populated by openpilot, and the rest will be done manually

This will be super information dense, so I imagine we'll need to move this to a webpage instead of a GitHub Markdown file.

These docs should also help make it clear when a car port is ready to supported and merged into upstream openpilot.

Related:

• commaai/openpilot#27320
• commaai/openpilot#26384