ci: use Apple silicon macOS runners (#5771)

Use the new Apple silicon macOS runner when running macOS tests.

While these new runners are twice as expensive as the normal macOS
runners, it is expected to be cost-neutral thanks to the speed increase.

For more information, see GitHub's announcement about the new runners:
https://github.blog/2023-10-02-introducing-the-new-apple-silicon-powered-m1-macos-larger-runner-for-github-actions/

.github/workflows/test.yml

@@ -12,15 +12,15 @@ jobs:
     name: Test
     strategy:
       matrix:
-        platform: [macos-latest]
+        platform: [macos-latest-xlarge]
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Checkout code
       uses: actions/checkout@v4
     - name: Set up Go 1.21
       uses: actions/setup-go@v4
       with:
-        go-version: "1.21.0"
+        go-version: "1.21"
         cache: true
     - name: Test
       run: make GO_TAGS="nodocker" test