[RSDK-14024] When cgo is present use trajex for the simulated arm

[acmorrow]

@dgottlieb - Opening this as a draft, for discussion and for you to be able to do local testing, not proposing that we merge it just yet.

This change demonstrates using trajex in the simulated arm by way of the trajex go bindings (viam-modules/trajex#15) and C api (viam-modules/trajex#14).

To build against this, you will need to:

1. Clone https://github.com/viam-modules/trajex somewhere local and change directories into the new clone
2. Configure (e.g. cmake -B build -S . -G Ninja) and build (e.g. cmake --build build --target all) the trajex libraries. Note that you must call the build directory build, and it must be at the root of the trajex tree.
3. Replace the RDK reference to trajex with the relative path from RDK to your local copy, with go mod edit -replace github.com/viam-modules/trajex=../trajex (update the replacement path as needed).

You should now be able to build and test the simulated arm using trajex: go test -count=1 ./components/arm/sim/...

If everything worked right, it should compile and link and you should be using the new trajectory generator.

Note that I'm still testing this, but I wanted to let you have an early look in case you had any feedback on the shape of things. I'll let you know once I'm happy with it, and then you should be able to experiment with invoking it from motion.

If we decide this is the right direction, then we can start figuring out what our production build and release story ought to look like.

[acmorrow]

@dgottlieb - Forgot to mention that if you want a smaller faster build for trajex, you can add -DVIAM_TRAJEX_BUILD_TESTS=OFF -DVIAM_TRAJEX_ENABLE_LEGACY=OFF -DVIAM_TRAJEX_ENABLE_TOOLS=OFF -DVIAM_TRAJEX_ENABLE_SERVICE=OFF -DBUILD_SHARED_LIBS=ON to the first cmake (the generation step) above.

[dgottlieb]

Has all the right stuff. High level preference is to align with the upcoming arm API proposal and ideally instrument simarm with trajex for convenient comparison, but also let be able to control it without going through trajex. And not needing to wait for a config change observe that comparison. More detail on a random line of code.