[FEATURE REQUEST] Include `wasm-tools` in official Dockerfile-rust image

**Is your feature request related to a problem?** Current `fastly compute build` inside `Dockerfile-rust` occasionally warns: ``` failed to download latest wasm-tools release: failed to request GitHub metadata: 403 Forbidden ``` because the CLI tries to fetch `wasm-tools` from GitHub unauthenticated. **Describe the solution you'd like** Add a `cargo install wasm-tools --locked` step to the Dockerfile-rust so the binary is already on `$PATH`. Example: ```diff && rustup target add wasm32-wasip1 --toolchain ${RUST_TOOLCHAIN} \ && apt-get update && apt-get install -y curl jq && apt-get -y clean && rm -rf /var/lib/apt/lists/* \ + && cargo install wasm-tools --locked \ && export FASTLY_CLI_VERSION=$(curl -s https://api.github.com/repos/fastly/cli/releases/latest ... ``` This makes `fastly compute build` fully offline and removes the 403 noise. **Describe alternatives you've considered** * Authenticate GitHub API requests via `GITHUB_TOKEN` (not ideal for a public image) * Ignore the warning (works but confusing for new users) **Additional context** Adding `wasm-tools` increases build time slightly but eliminates the external dependency and makes builds reproducible in CI/CD.