ci: refactor self-hosted runner configuration to use JSON format

- Convert runs-on array syntax to single runner value with fromjson()
- Update runner parameter defaults to JSON string format
- Add runner labels to build workflow calls
- Update test workflow runner configurations
- Remove unused test-utils.yml workflow

.github/workflows/_build_linux_self_host.yml

@@ -27,7 +27,7 @@ on:
         description: "Runner type"
         required: false
         type: string
-        default: "self-hosted"
+        default: '["self-hosted"]'
       is-upload:
         description: "Whether to upload the release asset"
         required: false
@@ -48,9 +48,7 @@ jobs:
   build_wheels_self_hosted:
     if: ${{ inputs.use-container }}
     name: Build wheels and Upload (Linux x86_64, self-hosted runner)
-    runs-on:
-      - ${{ inputs.runner }}
-      - x64
+    runs-on: ${{ fromjson(inputs.runner) }}
     container:
       image: ${{ inputs.container-image }}
     defaults:
@@ -187,9 +185,7 @@ jobs:
   build_wheels_self_hosted_no_container:
     if: ${{ !inputs.use-container }}
     name: Build wheels and Upload (Linux x86_64, self-hosted runner)
-    runs-on:
-      - ${{ inputs.runner }}
-      - x64
+    runs-on: ${{ fromjson(inputs.runner) }}
     defaults:
       run:
         shell: bash