Support pinning java-version as "latest"

Add a `latest` alias for the `java-version` input that floats to the newest
available stable (GA) release. It is normalized to the SemVer wildcard at the
base-installer layer and always resolves from remote (like `check-latest: true`).

List-based distributions resolve it automatically via the existing newest-first
matching. Corretto selects its newest available major; Oracle and GraalVM look up
the newest GA major via the Adoptium API and request it, failing with an actionable
error if that major isn't published yet. The jdkfile distribution rejects `latest`.

Closes #832

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

__tests__/distributors/oracle-installer.test.ts

@@ -174,3 +174,59 @@ describe('findPackageForDownload', () => {
     );
   });
 });
+describe('findPackageForDownload with latest', () => {
+  let spyHttpClientHead: any;
+  let spyHttpClientGetJson: any;
+
+  beforeEach(() => {
+    (core.debug as jest.Mock).mockImplementation(() => {});
+    (core.error as jest.Mock).mockImplementation(() => {});
+    spyHttpClientGetJson = jest.spyOn(HttpClient.prototype, 'getJson');
+    spyHttpClientGetJson.mockResolvedValue({
+      statusCode: 200,
+      result: {most_recent_feature_release: 25},
+      headers: {}
+    });
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  it('resolves the newest major version from the Adoptium API', async () => {
+    spyHttpClientHead = jest.spyOn(HttpClient.prototype, 'head');
+    spyHttpClientHead.mockResolvedValue({message: {statusCode: 200}});
+
+    const distribution = new OracleDistribution({
+      version: 'latest',
+      architecture: 'x64',
+      packageType: 'jdk',
+      checkLatest: false
+    });
+
+    const result = await distribution['findPackageForDownload']('x');
+    const osType = distribution.getPlatform();
+    const archiveType = getDownloadArchiveExtension();
+
+    expect(result.version).toBe('25');
+    expect(result.url).toBe(
+      `https://download.oracle.com/java/25/latest/jdk-25_${osType}-x64_bin.${archiveType}`
+    );
+  });
+
+  it('throws an actionable error when the latest major is not yet available', async () => {
+    spyHttpClientHead = jest.spyOn(HttpClient.prototype, 'head');
+    spyHttpClientHead.mockResolvedValue({message: {statusCode: 404}});
+
+    const distribution = new OracleDistribution({
+      version: 'latest',
+      architecture: 'x64',
+      packageType: 'jdk',
+      checkLatest: false
+    });
+
+    await expect(distribution['findPackageForDownload']('x')).rejects.toThrow(
+      /is not yet available for the Oracle JDK distribution/
+    );
+  });
+});