fix(core): Use more checked arithmetic, part 2b

[andyleiserson]

Follow-up to #9363 to address comments and add changelog entry.

This changes align_to to always panic if it would overflow (and removes assertions that did that in specific instances). Other than that, it should just be changing error reporting behavior.

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.