Enable RawSyntax validation and alternate token introspection in GitHub Actions

Author: ahoppen

.github/workflows/pull_request.yml

@@ -11,6 +11,12 @@ jobs:
     with:
       # https://github.com/swiftlang/swift-syntax/issues/2992
       enable_windows_checks: false
+      linux_env_vars: |
+        SWIFTSYNTAX_ENABLE_RAWSYNTAX_VALIDATION=1
+        SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION=1
+      windows_env_vars: |
+        SWIFTSYNTAX_ENABLE_RAWSYNTAX_VALIDATION=1
+        SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION=1
   soundness:
     name: Soundness
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main