Shard ty walltime benchmarks (#20791)

.github/workflows/ci.yaml

@@ -995,12 +995,16 @@ jobs:
           token: ${{ secrets.CODSPEED_TOKEN }}
 
   benchmarks-walltime:
+    name: "benchmarks walltime (${{ matrix.benchmarks }})"
     runs-on: codspeed-macro
     needs: determine_changes
     if: ${{ github.repository == 'astral-sh/ruff' && !contains(github.event.pull_request.labels.*.name, 'no-test') && (needs.determine_changes.outputs.ty == 'true' || github.ref == 'refs/heads/main') }}
     timeout-minutes: 20
-    env:
-      TY_LOG: ruff_benchmark=debug
+    strategy:
+      matrix:
+        benchmarks:
+          - "medium|multithreaded"
+          - "small|large"
     steps:
       - name: "Checkout Branch"
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
@@ -1030,5 +1034,5 @@ jobs:
           CODSPEED_PERF_ENABLED: false
         with:
           mode: walltime
-          run: cargo codspeed run
+          run: cargo codspeed run --bench ty_walltime "${{ matrix.benchmarks }}"
           token: ${{ secrets.CODSPEED_TOKEN }}