feat: add Rust build caching to ci-lazer-solana workflow (#64)

- Add cache-workspaces parameter to actions-rust-lang/setup-rust-toolchain@v1
- Cache target/ directory using Cargo.lock hash as cache key
- Follows same pattern as other lazer workflows in pyth-examples
- Improves build performance by caching compiled dependencies

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Jayant <jayant@dourolabs.xyz>

Author: devin-ai-integration[bot]

.github/workflows/ci-lazer-solana.yml

@@ -18,6 +18,7 @@ jobs:
         with:
           toolchain: 1.81.0
           components: clippy, rustfmt
+          cache-workspaces: "lazer/solana -> target"
       - name: install extra tools
         run: |
           cargo install --locked taplo-cli@0.9.3