chore(rust): prepare 2.0.0 release

[Seth Juarez (sethjuarez)]

Summary

• Promote Rust crates to stable 2.0.0 to match the Python package release
• Apply the Rust dependency updates from chore(deps): bump the cargo-version group in /runtime/rust with 8 updates #530 and migrate Foundry Entra auth to Azure Identity 1.0 APIs
• Switch OpenAI image defaults/tests from deprecated DALL-E usage to gpt-image-1
• Keep turn/tool behavior governed by shared Typra vectors and align Rust tool fixtures with the generated model shape
• Add PR-driven Rust release support via the release: rust label while preserving the existing rust/* tag workflow
• Add cargo package --workspace --locked as a publish preflight and sync gpt-image-1 capability snapshots across runtimes

Validation

• cargo check --workspace --all-targets
• cargo check --workspace --all-targets --all-features
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• cargo test --workspace --all-features
• cargo package --workspace --allow-dirty
• cargo package --workspace --locked --allow-dirty
• cargo test --workspace -- --ignored --test-threads=1
• cargo test -p prompty-foundry --features entra_id --test entra_id -- --ignored --test-threads=1
• python scripts\release.py --dry-run
• git --no-pager diff --check

Release notes

After this PR merges, add the release: rust label before merge to exercise the PR-driven release path. The workflow will create rust/2.0.0 from the merge commit and publish the Rust crates to crates.io using CARGO_REGISTRY_TOKEN.