Make Image & Mesh3D archetypes in Rust eager serialized

[Wumpf]

Related

• sister PR to..
  • Make Pinhole archetype in Rust eager serialized #8789
  • Make Box/AssetVideo/ViewCoordinates/Asset3D eager serialized in Rust #8785
• Fixes Allow archetypes to clear and/or update existing components #3381
• Fixes Eager/early serialize of components to arrow in Rust and C++ #7245

( fixes only if #8789 lands as well)

What

Similar to the previous PRs. These two had a few touching points, so this comes in bulk.
Led actually to a few nice cleanups around Meshes. Image cache on the other hand got a little bit hairy, resolved this by moving some extensions from the archetype down to the components.

No breaking changes & deprecations.

Next step: Remove "attr.rust.archetype_eager", making this always on.

• pass full check ci

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Result	Commit	Link	Manifest
✅	64258c2	https://rerun.io/viewer/pr/8793	+nightly +main

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[Wumpf]

oops, some todos left in there that indicate I wanted to test some stuff there first

[Wumpf]

indeed testing with raw_mesh rust example unearthed some issues!