Adopt swiftlang soundness workflow

Replaces our lint workflow with a more general solution from the swiftlang/github-workflow repo.

Author: rauhul

.github/workflows/lint.yml

@@ -7,22 +7,25 @@ on:
     branches: ["main"]
 
 jobs:
-  lint:
-    name: Lint
+  validate_format_config:
+    name: Validate Format Config
     runs-on: ubuntu-latest
-    container: swift:6.0-jammy
-
     steps:
       - name: Checkout repo
         uses: actions/checkout@v4
 
       - name: Install apt dependencies
-        run: apt-get -qq update && apt-get -qq -y install curl
+        run: sudo apt-get -qq update && sudo apt-get -qq -y install curl
 
       - name: Compare against swift-mmio swift-format config
         run: |
-          curl -sL https://raw.githubusercontent.com/apple/swift-mmio/refs/heads/main/SupportingFiles/Tools/swift-format/.swift-format -o .swift-format-mmio
+          curl -sL https://raw.githubusercontent.com/apple/swift-mmio/refs/heads/main/.swift-format -o .swift-format-mmio
           diff .swift-format .swift-format-mmio
 
-      - name: Lint
-        run: swift-format lint --recursive --strict .
+  soundness:
+    name: Soundness
+    uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
+    with:
+      api_breakage_check_enabled: false  # this repo doesn't vend any API
+      license_header_check_enabled: false  # feature: https://github.com/swiftlang/github-workflows/issues/78
+      license_header_check_project_name: "Swift.org"  # bug: https://github.com/swiftlang/github-workflows/issues/76