Migrate test policies to Rego v1

[dakshhhhh16]

Summary

This PR migrates Minder's embedded Rego test fixtures, sample rule YAML, and Rego docs examples to Rego v1 syntax as part of Phase 2 of #5262. (Parent issue)
Child issue #6463

The production evaluator already supports Rego version detection. This change moves the policy corpus we own toward the Rego v1 baseline by replacing v0 syntax and future.keywords examples with import rego.v1.

What changed

• Migrated embedded Rego snippets in evaluator and rtengine tests to Rego v1 syntax.
• Updated Minder sample/fixture rule YAML and quickstart policy YAML to import rego.v1.
• Updated Rego documentation snippets to stop recommending future.keywords imports.
• Refreshed the affected mindpak fixture hash after the YAML policy migration.

Validation

• git diff --check
• go test ./pkg/mindpak ./internal/engine/eval/... ./pkg/engine/v1/rtengine ./pkg/api/protobuf/go/minder/v1 ./cmd/cli/app/ruletype ./cmd/cli/app/quickstart
• go test ./... was also attempted. It reaches unrelated failures in internal/engine/actions/remediate/pull_request where tests cannot create a temporary git repository in this local environment.

Notes for reviewers

This is intended to be a syntax-only migration. The remaining v0 snippets in internal/engine/eval/rego/version_test.go are deliberate detector coverage and do not use future.keywords.

[coveralls]

Coverage is 60.446% — dakshhhhh16:rego-v1-test-policy-migration into mindersec:main. No base build found for mindersec:main.