Make ObjectId structure and invariants idiomatic

[teoxoy]

Checklist

• Run cargo clippy.
• Run RUSTFLAGS=--cfg=web_sys_unstable_apis cargo clippy --target wasm32-unknown-unknown if applicable.
• Add change to CHANGELOG.md. See simple instructions inside file.

Connections

Description

• disable the expose-ids feature by default (also fix compilation errors)
• make ObjectId structure and invariants idiomatic
• fix global_id always being 0 with the direct backend

Testing

[codecov-commenter]

Codecov Report

Merging #3347 (51058a3) into master (71f5040) will increase coverage by 0.08%.
The diff coverage is 76.92%.

❗ Current head 51058a3 differs from pull request most recent head deb0a13. Consider uploading reports for the commit deb0a13 to get more accurate results

@@            Coverage Diff             @@
##           master    #3347      +/-   ##
==========================================
+ Coverage   64.43%   64.51%   +0.08%     
==========================================
  Files          86       86              
  Lines       42638    42597      -41     
==========================================
+ Hits        27473    27481       +8     
+ Misses      15165    15116      -49     

Impacted Files	Coverage Δ
wgpu-core/src/id.rs	84.84% <ø> (+2.49%)	⬆️
wgpu/src/lib.rs	52.58% <ø> (+1.35%)	⬆️
wgpu/src/context.rs	53.32% <66.66%> (+0.04%)	⬆️
wgpu/src/backend/direct.rs	56.87% <100.00%> (+0.05%)	⬆️

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[cwfitzgerald]

Nice cleanup - could probably use a test, but that doesn't need to be in this PR