Impl bytemuck traits for geometry types

[CAD97]

Adds impls for bytemuck::Zeroable and bytemuck::Pod to the na::geometry::* types that don't already have them. All added impls just fully gate themselves on the fields' impls for these traits, so they should all be sound, unless I missed one of the following conditions:

• The type has invalid values (semantically, in which case the traits shouldn't be impl'd); or
• The type is not stable layout (#[repr(C)] or #[repr(transparent)]; or
• The type is stable layout but may have padding (for any value of T or other type parameters)

I believe this should reasonably close #830.

[sebcrozet]

Thank you for this PR! The CI is currently failing because some of the impls are missing trait-bounds.

[CAD97]

That's what I get for not checking --all-features 😅

Some places that are bounded on RealField could probably be loosened further to just Scalar, but that should probably wait until merged with #932.

[CAD97]

Resolved merge conflicts; should be good to merge.

[sebcrozet]

Thanks!