Ensure the limit for storage binding size honors alignment

[andyleiserson]

The CTS is not forgiving of the difference between 2^n - 1 and 2^n - 4.

I have also extracted some clamping that should probably be the same for all backends to auxil::apply_hal_limits, and filed a maintainability concern about the Metal backend as #8715.

Testing
Enables a relevant CTS test.

Squash or Rebase? Squash

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.