Migrates e2e tests from spock to plain JUnit

Per rationale in #3135, this migrates from groovy/spock to
Java/JUnit/AssertJ. This reduces the complexity of the project and its
dependencies, and makes an easier migration to JUnit Jupiter. Finally,
it eliminates the need for people to learn Groovy only to maintain
tests.

Signed-off-by: Adrian Cole <[email protected]>

Author: codefromthecrypt

e2e/pom.xml

@@ -13,9 +13,6 @@
         <relativePath>../pom.xml</relativePath>
     </parent>
 
-    <properties>
-        <spock.version>2.3-groovy-4.0</spock.version>
-    </properties>
     <dependencies>
         <dependency>
             <groupId>io.kubernetes</groupId>
@@ -28,12 +25,6 @@
             <version>${project.version}</version>
         </dependency>
 
-        <dependency>
-            <groupId>org.spockframework</groupId>
-            <artifactId>spock-core</artifactId>
-            <version>${spock.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
@@ -57,21 +48,6 @@
             <version>${slf4j.version}</version>
             <scope>test</scope>
         </dependency>
-
-        <!-- Following two deps exist to make spock2 work with junit4 -->
-        <!-- Ref: https://github.com/groovy/GMavenPlus/wiki/Examples#spock-2-and-junit -->
-        <dependency>
-            <groupId>org.junit.vintage</groupId>
-            <artifactId>junit-vintage-engine</artifactId>
-            <version>5.10.2</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.spockframework</groupId>
-            <artifactId>spock-junit4</artifactId>
-            <version>${spock.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.awaitility</groupId>
             <artifactId>awaitility</artifactId>
@@ -97,24 +73,6 @@
                     </systemPropertyVariables>
                 </configuration>
             </plugin>
-            <plugin>
-                <groupId>org.codehaus.gmavenplus</groupId>
-                <artifactId>gmavenplus-plugin</artifactId>
-                <executions>
-                    <execution>
-                        <goals>
-                            <goal>compileTests</goal>
-                        </goals>
-                    </execution>
-                </executions>
-                <dependencies>
-                    <dependency>
-                        <groupId>org.codehaus.groovy</groupId>
-                        <artifactId>groovy-all</artifactId>
-                        <version>2.4.21</version>
-                    </dependency>
-                </dependencies>
-            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-deploy-plugin</artifactId>