Disable collisions between attached bodies

[azeey]

🦟 Bug fix

Fixes #

Summary

Even with #632 , it looks like objects that are attached to each other continue to generate contacts. Even though we've explicitly marked the two objects not to collide, looking at the bullet code (https://github.com/bulletphysics/bullet3/blob/e9c461b0ace140d5c73972760781d94b7b5eee53/src/BulletDynamics/Featherstone/btMultiBodyLinkCollider.h#L79-L80), that is ignored because checkCollideWithOverride will always return true if the two objects are not in the same btMultiBody.

@iche033 I haven't checked this thoroughly, but the solution I came up with is to call the base class's checkCollideWithOverride as well as btMultiBodyLinkCollider::checkCollideWithOverride and return the result of anding the two. This does behave much better. I tried with the SDF below by uncommenting only one of the <plugin> tags. Without this PR, the objects fly up or down together even though gravity is 0. Visualizing contacts in gz-sim also shows that they are in contact. With the PR, the boxes stay in place and generate no contacts.

SDF File

```xml 0 0 0 true 0 0 1 0 0 1 100 100 0.8 0.8 0.8 1 0.8 0.8 0.8 1 0.8 0.8 0.8 1 0 2 3.0 0 0.0 0.0 1 1 0.5 1 1 0.5 1 0 0 1 1 0 0 1 1 0 0 1 body M2 body2 0.3 2 3.0 0 0.0 0 1 1 0.5 1 1 0.5 0 1 0 1 0 1 0 1 1 0 0 1 ```

Checklist

• [ ] Signed all commits for DCO
• [ ] Added tests
• [ ] Updated documentation (as needed)
• [ ] Updated migration guide (as needed)
• [ ] Consider updating Python bindings (if the library has them)
• [ ] codecheck passed (See contributing)
• [ ] All tests passed (See test coverage)
• [ ] While waiting for a review on your PR, please help review another open pull request to support the maintainers

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