ci: use setup-java to install multiple JDKs

Author: ktoso

.github/workflows/pull_request.yml

@@ -23,7 +23,9 @@ jobs:
         swift_version: ['6.1.2']
         os_version: ['jammy']
         jdk_vendor: ['corretto']
-        jdk_version: ['21']
+        jdk_version: | # install JDK21 for Gradle to use, and 24 for our runtime; 21 must be last to be "default" JAVA_HOME
+          24
+          21
     container:
       image: ${{ (contains(matrix.swift_version, 'nightly') && 'swiftlang/swift') || 'swift' }}:${{ matrix.swift_version }}-${{ matrix.os_version }}
     env:
@@ -49,7 +51,8 @@ jobs:
         swift_version: ['6.1.2']
         os_version: ['macos']
         jdk_vendor: ['corretto']
-        jdk_version: ['21']
+        jdk_version: ['24']
+        jdk_version_gradle: ['21']
     env:
       JAVA_HOME: "/usr/lib/jvm/default-jdk"
       SWIFT_JAVA_VERBOSE: true
@@ -73,7 +76,8 @@ jobs:
         swift_version: ['6.1.2']
         os_version: ['jammy']
         jdk_vendor: ['corretto']
-        jdk_version: ['21']
+        jdk_version: ['24']
+        jdk_version_gradle: ['21']
     container:
       image: ${{ (contains(matrix.swift_version, 'nightly') && 'swiftlang/swift') || 'swift' }}:${{ matrix.swift_version }}-${{ matrix.os_version }}
     env:
@@ -97,7 +101,8 @@ jobs:
         swift_version: ['6.1.2']
         os_version: ['macos']
         jdk_vendor: ['corretto']
-        jdk_version: ['21']
+        jdk_version: ['24']
+        jdk_version_gradle: ['21']
     env:
       JAVA_HOME: "/usr/lib/jvm/default-jdk"
       SWIFT_JAVA_VERBOSE: true
@@ -119,7 +124,8 @@ jobs:
         swift_version: ['6.1.2']
         os_version: ['jammy']
         jdk_vendor: ['corretto']
-        jdk_version: ['21']
+        jdk_version: ['24']
+        jdk_version_gradle: ['21']
         sample_app: [
           'JavaDependencySampleApp',
           'JavaKitSampleApp',
@@ -148,7 +154,8 @@ jobs:
         swift_version: ['6.1.2']
         os_version: ['macos']
         jdk_vendor: ['corretto']
-        jdk_version: ['21']
+        jdk_version: ['24']
+        jdk_version_gradle: ['21']
         sample_app: [
           'JavaDependencySampleApp',
           'JavaKitSampleApp',