Add getter for Schema to Validator

[cdisselkoen]

Description of changes

Allows callers who have already constructed a Validator, to take advantage of the getters on Schema (and its Protobuf trait implementation). This is necessary because constructing a Validator consumes the Schema.

Issue #, if available

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• A backwards-compatible change requiring a minor version bump to cedar-policy (e.g., addition of a new API).

I confirm that this PR (choose one, and delete the other options):

• Updates the "Unreleased" section of the CHANGELOG with a description of my change (required for major/minor version bumps).

I confirm that cedar-spec (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar formal model or DRT infrastructure.

I confirm that docs.cedarpolicy.com (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar language specification.

[github-actions]

Coverage Report

Head Commit: 58708367c0abc3ec1df097dd3cfa3ed86d63b757

Base Commit: 81ef1f5644d9a8be89f523339a1b1058f247560f

Download the full coverage report.

Coverage of Added or Modified Lines of Rust Code

Required coverage: 80.00%

Actual coverage: 0.00%

Status: FAILED ❌

Details

File	Status	Covered	Coverage	Missed Lines
cedar-policy-validator/src/lib.rs	🔴	0/3	0.00%	108-110
cedar-policy/src/api.rs	🔴	0/3	0.00%	1322-1324

Coverage of All Lines of Rust Code

Required coverage: 80.00%

Actual coverage: 80.75%

Status: PASSED ✅

Details

Package	Status	Covered	Coverage	Base Coverage
cedar-policy	🔴	3059/4395	69.60%	69.65%
cedar-policy-cli	🔴	539/927	58.14%	58.14%
cedar-policy-core	🟢	11328/13778	82.22%	82.23%
cedar-policy-formatter	🟢	914/1043	87.63%	87.63%
cedar-policy-validator	🟢	8242/9650	85.41%	85.44%
cedar-wasm	🔴	0/29	0.00%	0.00%