Introduce re_types_core

[teh-cmc]

This PR introduces a new crate: re_types_core.

re_types_core only contains the fundamental traits and types that make up Rerun's data model.
It is split off from the existing re_types.

This makes it possible to work with our data model abstractions without having to depend on the re_types behemoth.
This is more than a DX improvement: since so many things depend directly or indirectly on re_types, it is very easy to end-up with unsolvable dependency cycles. This helps with that in some cases (though certainly not all).

In particular, re_tuid (and by extension re_format) are now completely free of re_types.

For convenience, re_types reexports all of re_types_core, so the public API looks unchanged.
In a handful of instances (re_arrow_store, re_data_store, re_log_types, re_query), I've went the extra mile and started porting these crates towards raw re_types_core rather than relying on the reexports.
The reason is that, upon closer inspection, these crates are very close to being able to live free of re_types. In the future, the custom crate and custom module attributes coming with #3741 might allow us to make these independent.

Similarly, the codegen now uses re_types_core directly, as that makes the life of the upcoming "serde-codegen" work much easier.

What

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[Wumpf]

just because I was curious, here's the dependency graph for this branch

[Wumpf]

mostly only looked at toml and md files

I like where this is going: This should also make python and rerun_c a lot smaller once re_sdk is free of built-in types other than re_types_core 👍