Update Mockito to 5.23.0 for Java 25 support

Mockito 5.17.0 bundled ByteBuddy 1.15.11 which does not support Java 25
class files, causing SchedulerShutdownRaceTest and ZeroTimeoutContractTest
to fail with 'Mockito cannot mock this class'.

- Upgrade mockito-core from 5.17.0 to 5.23.0 (includes ByteBuddy 1.17.5+)
- Add JDK 21+ profile that passes -XX:+EnableDynamicAgentLoading to
  Surefire, allowing Mockito/ByteBuddy to attach at runtime (JEP 451)
- Use a default-empty surefire.jvm.args property so JDK 17-20 are
  unaffected by the flag

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

Author: brunoborges

pom.xml

@@ -51,6 +51,8 @@
         <copilot.tests.dir>${copilot.sdk.clone.dir}/test</copilot.tests.dir>
         <!-- Set to true (via -Pskip-test-harness) to skip git-clone + npm install of test harness -->
         <skip.test.harness>false</skip.test.harness>
+        <!-- Extra JVM args for Surefire; overridden by the jdk21+ profile -->
+        <surefire.jvm.args />
     </properties>
 
     <dependencies>
@@ -89,7 +91,7 @@
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
-            <version>5.17.0</version>
+            <version>5.23.0</version>
             <scope>test</scope>
         </dependency>
     </dependencies>
@@ -245,8 +247,8 @@
                 <artifactId>maven-surefire-plugin</artifactId>
                 <version>3.5.4</version>
                 <configuration>
-                    <!-- Inject JaCoCo agent for coverage collection during test runs -->
-                    <argLine>${testExecutionAgentArgs}</argLine>
+                    <!-- Inject JaCoCo agent + any JDK-version-specific flags -->
+                    <argLine>${testExecutionAgentArgs} ${surefire.jvm.args}</argLine>
                     <systemPropertyVariables>
                         <copilot.tests.dir>${copilot.tests.dir}</copilot.tests.dir>
                         <copilot.sdk.dir>${copilot.sdk.clone.dir}</copilot.sdk.dir>
@@ -543,6 +545,18 @@
     </reporting>
 
     <profiles>
+        <!-- Enable dynamic agent loading on JDK 21+ so Mockito/ByteBuddy
+             can attach at runtime (JEP 451). The flag does not exist on
+             earlier JDKs, so it must be conditional. -->
+        <profile>
+            <id>jdk21+</id>
+            <activation>
+                <jdk>[21,)</jdk>
+            </activation>
+            <properties>
+                <surefire.jvm.args>-XX:+EnableDynamicAgentLoading</surefire.jvm.args>
+            </properties>
+        </profile>
         <!-- Skip git-clone + npm install of the copilot-sdk test harness -->
         <profile>
             <id>skip-test-harness</id>