Add CLDC11 compatibility check workflow and APIChecker tool

This change introduces a new GitHub Actions pipeline (`.github/workflows/cldc11-check.yml`) that verifies `Ports/CLDC11` is a binary compatible subset of JavaSE 11 and `vm/JavaAPI`.

It also adds a custom tool `scripts/api-checker`, implemented in Java using ASM, to perform the binary compatibility analysis (checking classes, methods, fields, superclasses, and interfaces). The tool generates a report of extra APIs present in the reference (e.g., `vm/JavaAPI`) as requested.

The workflow is configured to run on JDK 11 to support the tool's usage of modern Java APIs (like `InputStream.readAllBytes` and `jrt:/` filesystem). Explicit permissions are set for the workflow.

Author: google-labs-jules[bot]

.github/workflows/cldc11-check.yml

@@ -6,12 +6,17 @@ on:
       - 'Ports/CLDC11/**'
       - 'vm/JavaAPI/**'
       - '.github/workflows/cldc11-check.yml'
+    branches:
+      - master
   pull_request:
     paths:
       - 'Ports/CLDC11/**'
       - 'vm/JavaAPI/**'
       - '.github/workflows/cldc11-check.yml'
 
+permissions:
+  contents: read
+
 jobs:
   check-cldc11:
     runs-on: ubuntu-latest
@@ -26,7 +31,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Build APIChecker
-        run: mvn package -f scripts/api-checker/pom.xml
+        run: JAVA_HOME=$JAVA11_HOME mvn package -f scripts/api-checker/pom.xml
 
       - name: Build Ports/CLDC11
         run: |