[naga] Fix issues with const evaluation of bitwise shifts

[andyleiserson]

Fixes two issues with const evaluation of bitwise shifts:

• Disallows mixed scalar/vector shifts (scalar << vector or vector << scalar), which should not be allowed.
• Detects overflowing runtime << constant shifts at constant evaluation time.

Also includes, as a separate commit, cleanup of some noisy log messages in the naga expression validator.

Testing
Enables CTS tests.

Squash or Rebase? Rebase

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

[teoxoy]

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