Build test policies in CI

[JustusAdam]

What Changed?

Adds a build step for props in rust.yml

Why Does It Need To?

Before you could make breaking changes to the interface of our crates. Now at least we'll see them in the test properties.

Checklist

• Above description has been filled out so that upon quash merge we have a
  good record of what changed.
• New functions, methods, types are documented. Old documentation is updated
  if necessary
• Documentation in Notion has been updated
• Tests for new behaviors are provided
  • New test suites (if any) ave been added to the CI tests (in
    .github/workflows/rust.yml) either as compiler test or integration test.
    Or justification for their omission from CI has been provided in this PR
    description.