feat: Add set-default option (#1017)

* Add set-default option

This option allows to install an additional JDK without making it the
default one.

I have wanted this for quite a long time as I'm running custom GitHub
Actions with Java, which might require a specific JDK and I don't want
to pollute the JDK that is used by the overall workflow calling the
action.
And I'm apparently not alone as there was a preexisting issue.

Fixes #560

* Dedupe setJavaDefault and document multi-version/toolchain behavior

- Refactor setJavaDefault to delegate shared output/env logic to
  setJavaEnvironment, avoiding duplication between the two.
- Document that set-default applies to all JDKs in a multiline
  java-version, and that installed JDKs remain registered in Maven
  toolchains regardless of set-default.

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

* test: fix Prettier formatting in base-installer test

Resolves the failing 'Basic validation / build' format-check on
__tests__/distributors/base-installer.test.ts (line exceeded print width).

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

---------

Co-authored-by: Bruno Borges <brborges@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/setup-java.ts

@@ -29,6 +29,7 @@ async function run() {
       constants.INPUT_CACHE_DEPENDENCY_PATH
     );
     const checkLatest = getBooleanInput(constants.INPUT_CHECK_LATEST, false);
+    const setDefault = getBooleanInput(constants.INPUT_SET_DEFAULT, true);
     const verifySignature = getBooleanInput(
       constants.INPUT_VERIFY_SIGNATURE,
       false
@@ -51,6 +52,7 @@ async function run() {
       architecture,
       packageType,
       checkLatest,
+      setDefault,
       verifySignature,
       verifySignaturePublicKey,
       distributionName,
@@ -110,6 +112,7 @@ async function installVersion(
     architecture,
     packageType,
     checkLatest,
+    setDefault,
     verifySignature,
     verifySignaturePublicKey,
     toolchainIds
@@ -119,6 +122,7 @@ async function installVersion(
     architecture,
     packageType,
     checkLatest,
+    setDefault,
     verifySignature,
     verifySignaturePublicKey,
     version
@@ -155,6 +159,7 @@ interface installerInputsOptions {
   architecture: string;
   packageType: string;
   checkLatest: boolean;
+  setDefault: boolean;
   verifySignature: boolean;
   verifySignaturePublicKey: string | undefined;
   distributionName: string;