Handle changes in metadata types from EXT_mesh_features

[ptrgags]

Wait to merge this until #9872 is merged.

This PR is the second in a series to update our implementation to support both EXT_feature_metadata (old) and EXT_mesh_features (new).

This PR handles the difference in types between the two extensions:

• we simplified the types so individual values look similar to: type: SINGLE, componentType: FLOAT32
• we added dedicated VECn and MATn types for vectors/matrices.

This does NOT handle changing optional/default -> noData/required, that will be a follow-up PR since this one was already quite large.

[cesium-concierge]

Thanks for the pull request @ptrgags!

• ✔️ Signed CLA found.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.

[ptrgags]

Just checked the code coverage, it's pretty close, just a few places need additional tests

[ptrgags]

@sanjeetsuhag this is ready for review, just don't merge until #9872 is merged.

[ptrgags]

@sanjeetsuhag just synced with main to pull in the two PRs from yesterday.

[sanjeetsuhag]

The changes here look good. Tested loading of glTFs and tilesets with metadata and they are working fine. Coverage is fine too. The documentation needs a little work.

[ptrgags]

@sanjeetsuhag updated!

[sanjeetsuhag]

Latest commits look good. Thanks @ptrgags!

[lilleyse]

Now that vector and matrix types are supported natively, would it make sense to revert #9495?

[ptrgags]

@lilleyse no, we still need to unpack VECN and MATN, just not things like ARRAY[FLOAT32, N], this PR already accounts for that. See these lines: https://github.com/CesiumGS/cesium/pull/9880/files#diff-a559a016280a5baf661f1c19a79de91a848b919fe0f0b5ed3f44efd261009036L327-R366

[lilleyse]

Ah thanks for pointing me to that, I skimmed too fast 😄