Add nightly-6.3 to our PR CI workflow and pin all workflows to a specific tag (#1443)

This modifies our pull request GitHub Actions workflow which is
currently using `nightly-6.2` builds to add `nightly-6.3` as well. This
is possible now that [nightly 6.3 development
snapshots](https://forums.swift.org/t/swift-6-3-nightly-development-snapshots/83621)
are available and swiftlang/github-workflows#206
has added the necessary workflow support logic.

Additionally, this pins all of our workflows which
[use](https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#jobsjob_idstepsuses)
[swiftlang/github-workflows](https://github.com/swiftlang/github-workflows)
to a specific tag
([`0.0.2`](https://github.com/swiftlang/github-workflows/releases/tag/0.0.2))
instead of `main`. As of
swiftlang/github-workflows#196, this is now the
[recommended
practice](https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#jobsjob_idstepsuses)
since it helps prevent breakages due to upstream changes in the workflow
definition file.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: stmontgomery

.github/workflows/automerge.yml

@@ -18,7 +18,7 @@ on:
 jobs:
   create_merge_pr:
     name: Create PR to merge main into release branch
-    uses: swiftlang/github-workflows/.github/workflows/create_automerge_pr.yml@main
+    uses: swiftlang/github-workflows/.github/workflows/create_automerge_pr.yml@0.0.2
     with:
       head_branch: main
       base_branch: release/6.3

.github/workflows/main_using_main.yml

@@ -15,7 +15,7 @@ concurrency:
 jobs:
   tests:
     name: Test
-    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
+    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@0.0.2
     with:
       linux_swift_versions: '["nightly-main"]'
       linux_os_versions: '["amazonlinux2", "jammy"]'

.github/workflows/main_using_release.yml

@@ -15,7 +15,7 @@ concurrency:
 jobs:
   tests:
     name: Test
-    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
+    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@0.0.2
     with:
       linux_swift_versions: '["nightly-6.2"]'
       linux_os_versions: '["amazonlinux2", "jammy"]'

.github/workflows/pull_request.yml

@@ -14,11 +14,11 @@ concurrency:
 jobs:
   tests:
     name: Test
-    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
+    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@0.0.2
     with:
-      linux_swift_versions: '["nightly-main", "nightly-6.2"]'
+      linux_swift_versions: '["nightly-main", "nightly-6.3", "nightly-6.2"]'
       linux_os_versions: '["amazonlinux2", "jammy"]'
-      windows_swift_versions: '["nightly-main", "nightly-6.2"]'
+      windows_swift_versions: '["nightly-main", "nightly-6.3", "nightly-6.2"]'
       enable_macos_checks: true
       macos_exclude_xcode_versions: '[{"xcode_version": "16.2"}, {"xcode_version": "16.3"}, {"xcode_version": "16.4"}]'
       enable_ios_checks: true
@@ -27,7 +27,7 @@ jobs:
       enable_android_sdk_build: true
   soundness:
     name: Soundness
-    uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
+    uses: swiftlang/github-workflows/.github/workflows/soundness.yml@0.0.2
     with:
       license_header_check_project_name: "Swift"
       docs_check_enabled: false