Simplify Maven configuration by running DiktatSaveSmokeTest as an integration test (#1482)

### What's done:

 * Finally, fixes #1478.

Author: 0x6675636b796f75676974687562

diktat-rules/pom.xml

@@ -164,21 +164,71 @@
 
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-jar-plugin</artifactId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <excludes>
+                        <exclude>**/DiktatSaveSmokeTest.*</exclude>
+                    </excludes>
+                </configuration>
+            </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-failsafe-plugin</artifactId>
+                <configuration>
+                    <includes>
+                        <include>**/DiktatSaveSmokeTest.*</include>
+                    </includes>
+                </configuration>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>integration-test</goal>
+                            <goal>verify</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+
+            <plugin>
+                <groupId>org.jacoco</groupId>
+                <artifactId>jacoco-maven-plugin</artifactId>
                 <executions>
-                    <!-- Don't produce the JAR during the `package` phase. -->
+                    <!-- These executions complement those defined in the parent pom.xml. -->
                     <execution>
-                        <id>default-jar</id>
-                        <phase>none</phase>
+                        <id>default-prepare-agent-integration</id>
+                        <goals>
+                            <goal>prepare-agent-integration</goal>
+                        </goals>
                     </execution>
-                    <!-- Instead, create it immediately before the `test` phase
-                         so that the shade plug-in may use it. -->
                     <execution>
-                        <id>fat-jar-for-smoke-tests</id>
-                        <phase>process-test-classes</phase>
+                        <id>default-merge</id>
+                        <phase>post-integration-test</phase>
+                        <goals>
+                            <goal>merge</goal>
+                        </goals>
+                        <configuration>
+                            <fileSets>
+                                <fileSet>
+                                    <directory>${project.build.directory}</directory>
+                                    <includes>
+                                        <include>jacoco.exec</include>
+                                        <include>jacoco-it.exec</include>
+                                    </includes>
+                                </fileSet>
+                            </fileSets>
+                            <destFile>${project.build.directory}/jacoco-merged.exec</destFile>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>default-report-merged</id>
                         <goals>
-                            <goal>jar</goal>
+                            <goal>report-integration</goal>
                         </goals>
+                        <configuration>
+                            <outputDirectory>${project.reporting.outputDirectory}/jacoco</outputDirectory>
+                            <dataFile>${project.build.directory}/jacoco-merged.exec</dataFile>
+                        </configuration>
                     </execution>
                 </executions>
             </plugin>
@@ -188,7 +238,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-shade-plugin</artifactId>
-                <version>3.3.0</version>
                 <configuration>
                     <!-- Suppress the generation of `dependency-reduced-pom.xml`,
                          because it will also get installed under `~/.m2`,
@@ -221,7 +270,7 @@
                 <executions>
                     <execution>
                         <id>fat-jar-for-smoke-tests</id>
-                        <phase>process-test-classes</phase>
+                        <phase>package</phase>
                         <goals>
                             <goal>shade</goal>
                         </goals>

pom.xml

@@ -278,6 +278,11 @@
                     <artifactId>maven-failsafe-plugin</artifactId>
                     <version>3.0.0-M7</version>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-shade-plugin</artifactId>
+                    <version>3.3.0</version>
+                </plugin>
                 <plugin>
                     <groupId>org.codehaus.mojo</groupId>
                     <artifactId>versions-maven-plugin</artifactId>