ci: Alpine 3.24 musl container and move small-runner jobs to amd64-ci-medium (#10667)

- **musl container**: `rust:1-alpine3.21` → `rust:1-alpine3.24`. Alpine
3.21 is the oldest version the Rust image still publishes, and it
reaches end of life in November 2026.
- **`amd64-ci-small` → `amd64-ci-medium`** for the two jobs that used
the 4-CPU class: Rust docs and the "with tokio dispatcher" build. Once
the `.github-private` change lands, both get 8 CPUs. In #10653, Rust
docs went from 288s to 212–235s with 8 CPUs.

---------

Co-authored-by: Robert Kruszewski <github@robertk.io>

Author: joseph-isaacs

.github/workflows/ci.yml

@@ -327,7 +327,7 @@ jobs:
             runner: amd64-ci-large
             args: "--all-targets"
           - name: "with tokio dispatcher"
-            runner: amd64-ci-small
+            runner: amd64-ci-medium
             # Only build the crates that have the tokio features, not re-building other crates with no-default-features
             args: "--no-default-features --features tokio --all-targets -p vortex -p vortex-io -p vortex-file -p vortex-layout"
           - name: "wasm32 with default features"

.github/workflows/musl.yml

@@ -29,7 +29,7 @@ jobs:
           && format('runs-on={0}/runner=amd64-large/image=ubuntu24-full-x64-pre-v2/tag=rust-build-musl', github.run_id)
           || 'ubuntu-latest' }}
     container:
-      image: ghcr.io/rust-lang/rust:1-alpine3.21
+      image: ghcr.io/rust-lang/rust:1-alpine3.24
       credentials:
         username: ${{ github.repository_owner }}
         password: ${{ secrets.GITHUB_TOKEN }}