Forward Rust (de-)serialization of transparent datatypes

[Wumpf]

What

Remove lots of redundant serialization code by forwarding transparent components to its datatypes:

• forward from_arrow_opt for fully transparent types
• forward from_arrow for fully transparent types
  • this requires us generating it for datatypes!
  • the forwarding uses bytemuck when possible. Should be possible in more places, but the constraints are complicated so this isn't fully automated and depends on types being manually marked as bytemuck::Pod
    * would be really nice though if we could automate that. Almost everything we're dealing with should be pod 🤔
• forward to_arrow_opt for fully transparent types
• forward arrow_datatype for fully transparent types

@ reviewer: There's only two non-generated files:

• crates/re_types_builder/src/codegen/rust/api.rs: https://github.com/rerun-io/rerun/pull/6793/files#diff-4eb7d4aa8c72b1987ed00d1ad9c61782b9dd55d8b96a50a44156388fea8c67f9
• crates/re_types_builder/src/codegen/rust/deserializer.rs: https://github.com/rerun-io/rerun/pull/6793/files#diff-91844032ca93ef2e29de6a660674273bfd6e836b26ae58c83fef09dcd8db1076
  Everything else is generated via those changes. You'll want to have a sampling of both datatypes & components.

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[emilk]

Nice!

[Wumpf]

less lambdas, neat suggestions! :)