[Rust] Consolidate Cargo workspace and reorganize examples

[teodordelibasic-db]

What changes are proposed in this pull request?

• Moved Rust examples from rust/examples/ to examples/rust/ as standalone crates depending on the published SDK from crates.io, with the goal of simulating a real client that can just be copied from the repo.
• Consolidated 4 example crates into 2 (rust-json, rust-proto) with [[example]] targets batch and single, deduplicating the shared proto output/ directory
• Added [workspace.dependencies] to rust/Cargo.toml, centralizing 21 shared dependencies across workspace members
• Split CI: new ci-rust-examples.yml (fmt + clippy) runs only on examples/rust/** changes, independent from the main Rust workspace CI

How is this tested?

# Check Workspace
cargo check --workspace --all-targets --manifest-path rust/Cargo.toml
cargo test --workspace --manifest-path rust/Cargo.toml

# Check Examples
cargo check --manifest-path examples/rust/json/Cargo.toml --examples
cargo check --manifest-path examples/rust/proto/Cargo.toml --examples

# Run JSON
cargo run --manifest-path examples/rust/json/Cargo.toml --example batch
cargo run --manifest-path examples/rust/json/Cargo.toml --example single

# Run Proto
cargo run --manifest-path examples/rust/proto/Cargo.toml --example batch
cargo run --manifest-path examples/rust/proto/Cargo.toml --example single

[elenagaljak-db]

Looks very good and I think it will simplify usage a lot. Can you go through READMEs to see if we have any stale instructions on how to run examples?