Add version of resolved Pkl distribution to ExecutorException (#719)

* Add version of resolved Pkl distribution to `ExecutorException`

* Review comments

Co-authored-by: Daniel Chao <daniel.h.chao@gmail.com>

---------

Co-authored-by: Daniel Chao <daniel.h.chao@gmail.com>

pkl-executor/src/main/java/org/pkl/executor/EmbeddedExecutor.java

@@ -226,7 +226,7 @@ final class EmbeddedExecutor implements Executor {
       try {
         return executorSpi.evaluatePath(modulePath, options.toSpiOptions());
       } catch (ExecutorSpiException e) {
-        throw new ExecutorException(e.getMessage(), e.getCause());
+        throw new ExecutorException(e.getMessage(), e.getCause(), executorSpi.getPklVersion());
       } finally {
         currentThread.setContextClassLoader(prevContextClassLoader);
       }

pkl-executor/src/main/java/org/pkl/executor/ExecutorException.java

@@ -15,15 +15,44 @@
  */
 package org.pkl.executor;
 
+import java.util.Objects;
+
 /**
  * Indicates an {@link Executor} error. {@link #getMessage()} returns a user-facing error message.
  */
 public final class ExecutorException extends RuntimeException {
+  private final String pklVersion;
+
   public ExecutorException(String message) {
     super(message);
+    pklVersion = null;
   }
 
   public ExecutorException(String message, Throwable cause) {
     super(message, cause);
+    pklVersion = null;
+  }
+
+  public ExecutorException(String message, Throwable cause, String version) {
+    super(message, cause);
+    pklVersion = Objects.requireNonNull(version);
+  }
+
+  /**
+   * The selected Pkl version used to evaluate the module.
+   *
+   * <p>Returns {@code null} if this exception does not originate from an underlying Pkl evaluator.
+   */
+  public String getPklVersion() {
+    return pklVersion;
+  }
+
+  @Override
+  public String getMessage() {
+    var message = super.getMessage();
+    if (pklVersion == null) {
+      return message;
+    }
+    return message + "\nPkl version: " + pklVersion;
   }
 }