test(instrumentation): convert Spring boot test apps to simple Java apps

We do not actually need to start a whole framework with an HTTP server
to check one environment variable and exit.

Also:
- disable all auto-instrumentation by the Java agent for JVM
  instrumentation image tests
- remove Node.js 18 Bullseye base image for Node.js tests

All of this should help to speed up the instrumentation image tests.

images/instrumentation/test/jvm/Dockerfile

@@ -11,7 +11,12 @@ FROM ${test_image}
 COPY test-cases /test-cases
 COPY .m2 /.m2
 
-RUN for test in /test-cases/*; do (cd "/${test}" && JAVA_HOME=$(which java | xargs dirname | xargs dirname) "./mvnw" "-gs" "/.m2/settings.xml" package); done
+RUN export JAVA_HOME=$(which java | xargs dirname | xargs dirname)
+RUN for test in /test-cases/*; do \
+  cd "/${test}" && \
+  javac Main.java && \
+  jar -cfm app.jar MANIFEST.MF *.class \
+; done
 
 # The following lines emulate the behavior of running the instrumentation image as a Kubernetes init container and
 # setting the LD_PRELOAD environment variable via the operator.

images/instrumentation/test/jvm/test-cases/.gitignore

@@ -0,0 +1 @@
+*.class

images/instrumentation/test/jvm/test-cases/existing-unmodified/MANIFEST.MF

@@ -0,0 +1,2 @@
+Manifest-Version: 1.0
+Main-Class: Main

images/instrumentation/test/jvm/test-cases/existing-unmodified/Main.java

@@ -0,0 +1,9 @@
+public class Main {
+
+    public static void main(String[] args) {
+        String value = System.getenv("AN_ENVIRONMENT_VARIABLE");
+        if (!"value".equals(value)) {
+            throw new RuntimeException(String.format("Unexpected value for the 'AN_ENVIRONMENT_VARIABLE' env var: %s", value));
+        }
+    }
+}