Map Amazon Linux 2023 to amazonlinux2023 toolchain infix

Amazon Linux 2023 reports ID=amzn and VERSION_ID=2023 in
/etc/os-release. This combination fell through to the generic
else branch, producing the OS name amzn2023 and thus an invalid
Swift toolchain download URL (swift-...-amzn2023-aarch64.tar.gz),
causing a "Toolchain not found" failure. Special-case it to the
amazonlinux2023 infix that swift.org actually publishes.

Author: jakepetroules

.github/workflows/pull_request.yml

@@ -25,7 +25,7 @@ jobs:
     uses: ./.github/workflows/swift_package_test.yml
     with:
       # Linux
-      linux_os_versions: '["jammy", "rhel-ubi9", "amazonlinux2"]'
+      linux_os_versions: '["jammy", "rhel-ubi9", "amazonlinux2", "amazonlinux2023"]'
       linux_host_archs: '["x86_64", "aarch64"]'
       linux_build_command: |
         cd tests/TestPackage

.github/workflows/scripts/install-and-build-with-sdk.sh

@@ -485,6 +485,9 @@ initialize_os_info() {
     elif [[ "$os_id" == "amzn" && "$version_id" == "2" ]]; then
         OS_NAME="amazonlinux2"
         OS_NAME_NO_DOT="amazonlinux2"
+    elif [[ "$os_id" == "amzn" && "$version_id" == "2023" ]]; then
+        OS_NAME="amazonlinux2023"
+        OS_NAME_NO_DOT="amazonlinux2023"
     else
         # Ubuntu, Debian, Fedora
         OS_NAME="${os_id}${version_id}"