[SPARK-46476][BUILD][CORE][CONNECT] Move IvyTestUtils back to `src/…

…test` directory

### What changes were proposed in this pull request?
This pr move `IvyTestUtils` back to `src/test` directory because it has been in the `src/test` directory before the refactoring work of #43354.

Meanwhile, in order to make the `core` and `connect-client-jvm` module use `IvyTestUtils` in the tests, this pr has added the corresponding Maven dependencies in the respective `pom.xml` files.

### Why are the changes needed?
Move `IvyTestUtils` back to `src/test` directory

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
Pass GitHub Actions

### Was this patch authored or co-authored using generative AI tooling?
No

Closes #44440 from LuciferYang/mv-IvyTestUtils-to-test-dir.

Authored-by: yangjie01 <yangjie01@baidu.com>
Signed-off-by: yangjie01 <yangjie01@baidu.com>

connector/connect/client/jvm/pom.xml

@@ -82,6 +82,13 @@
       <artifactId>scalacheck_${scala.binary.version}</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.apache.spark</groupId>
+      <artifactId>spark-common-utils_${scala.binary.version}</artifactId>
+      <version>${project.version}</version>
+      <classifier>tests</classifier>
+      <scope>test</scope>
+    </dependency>
     <!-- Use mima to perform the compatibility check -->
     <dependency>
       <groupId>com.typesafe</groupId>

core/pom.xml

@@ -451,6 +451,13 @@
       <classifier>tests</classifier>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.apache.spark</groupId>
+      <artifactId>spark-common-utils_${scala.binary.version}</artifactId>
+      <version>${project.version}</version>
+      <classifier>tests</classifier>
+      <scope>test</scope>
+    </dependency>
 
     <!--
       This spark-tags test-dep is needed even though it isn't used in this module, otherwise testing-cmds that exclude