Add larod-sys

[JsGjKJzi]

Describe your changes

This adds the larod-sys crate as an initial step to adding a later larod crate.

The larod-sys crate contains mainly the code needed for bindgen to generate Rust wrappers around the larod.h header file. The few exceptions are where enums or constants are defined by function style C macros that bindgen does not handle. These enums or constants are defined manually in the larod-sys/src/lib.rs file.

Checklist before requesting a review

• I have performed a self-review of my own code
• I have verified that the code builds perfectly fine on my local system
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have verified that my code follows the style already available in the repository
• I have made corresponding changes to the documentation

[JsGjKJzi]

@apljungquist I'm getting some time again to work on this so trying to merge things in piecemeal. As you mentioned, enough changed between main and the prior Add Larod PR that I think it makes sense to pull smaller chunks of code out of that PR and merge them in individually.

[apljungquist]

Nice! I'd like to take time to understand and do a proper review, but let's see how that goes - the amount of time I can dedicate to this project is significantly reduced since I left Axis. But if I can't make time then at least I will try to get out of your way so we can get this contribution merged; together with VDO it is in my opinion the most important missing piece in the ACAP+Rust puzzle.