[CI] GitHub Actions support for PR testing and automerger

.github/workflows/automerge.yml

@@ -0,0 +1,23 @@
+name: Create PR to merge release into main branch
+# In the first period after branching the release branch,
+# we typically want to include many changes from `main` in the release branch.
+# This workflow automatically creates a PR to merge the release branch into the main.
+# Later in the release cycle we should stop this practice to avoid landing risky changes by disabling this workflow.
+# To do so, disable the workflow as described in https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-workflow-runs/disabling-and-enabling-a-workflow
+permissions:
+  contents: read
+on:
+  schedule:
+    - cron: '0 9 * * MON'
+  workflow_dispatch:
+jobs:
+  create_merge_pr:
+    name: Create PR to merge release into main branch
+    uses: swiftlang/github-workflows/.github/workflows/create_automerge_pr.yml@main
+    with:
+      head_branch: release/6.3
+      base_branch: main
+    permissions:
+      contents: write
+      pull-requests: write
+    if: (github.event_name == 'schedule' && github.repository == 'swiftlang/swift-tools-support-core') || (github.event_name != 'schedule')  # Ensure that we don't run this on a schedule in a fork

.github/workflows/pull_request.yml

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+name: Pull request
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  tests:
+    name: Test
+    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
+    with:
+      linux_os_versions: '["amazonlinux2", "bookworm", "noble", "jammy", "rhel-ubi9"]'
+      linux_swift_versions: '["nightly-main", "nightly-6.2"]'
+      windows_swift_versions: '["nightly-main"]'
+      enable_linux_static_sdk_build: true
+      enable_android_sdk_build: true
+      android_sdk_build_command: "swift build --build-tests"
+      android_ndk_versions: '["r27d", "r29"]'
+      enable_ios_checks: true
+      enable_macos_checks: true
+      macos_exclude_xcode_versions: "[{\"xcode_version\": \"16.3\"}, {\"xcode_version\": \"16.4\"}]"
+
+  soundness:
+    name: Soundness
+    uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
+    with:
+      license_header_check_project_name: "Swift"
+      api_breakage_check_enabled: false
+      format_check_enabled: false