[SPARK-53650] Make build.gradle and libs.versions.toml up-to-date with okhttp3 usage

### What changes were proposed in this pull request?

This PR aims to validate and update the Gradle build dependencies in terms of `okhttp3` library usage.

```
gradle/libs.versions.toml
spark-operator-api/build.gradle
spark-operator/build.gradle
```

### Why are the changes needed?

- As of now, `okhttp3` is a test dependency. So, we need to move `okhttp` to the test dependency section like `junit`.

https://github.com/apache/spark-kubernetes-operator/blob/b0d7d9592ba15b37c067657c929d44f9c2ff5d88/gradle/libs.versions.toml#L21-L27

- Since SPARK-52005, `Apache Spark K8s Operator` is using `Apache Spark 4` dependency which has no direct dependency to `okhttp3` library. So, we don't need the following exclusion.

https://github.com/apache/spark-kubernetes-operator/blob/b0d7d9592ba15b37c067657c929d44f9c2ff5d88/spark-operator/build.gradle#L69

- Since `Fabric8` v7.0.0, `VertxHttpClientFactory` is the default so that we don't need to exclude `okhttp3`. In addition, we migrated to use `VertxHttpClientFactory` via SPARK-53648.

https://github.com/apache/spark-kubernetes-operator/blob/b0d7d9592ba15b37c067657c929d44f9c2ff5d88/spark-operator-api/build.gradle#L20-L23

### Does this PR introduce _any_ user-facing change?

No behavior change.

### How was this patch tested?

Pass the CIs and manual check.

**BEFORE**

```
$ git grep okhttp
gradle/libs.versions.toml:okhttp = "4.12.0"
gradle/libs.versions.toml:okhttp = { group = "com.squareup.okhttp3", name = "okhttp", version.ref = "okhttp" }
gradle/libs.versions.toml:mockwebserver = { group = "com.squareup.okhttp3", name = "mockwebserver", version.ref = "okhttp" }
spark-operator-api/build.gradle:    exclude group: 'com.squareup.okhttp3'
spark-operator/build.gradle:    exclude group: 'com.squareup.okhttp3'
spark-operator/build.gradle:    exclude group: 'com.squareup.okhttp3'
spark-operator/build.gradle:    exclude group: 'com.squareup.okhttp3'
```

**AFTER**

```
$ git grep okhttp
gradle/libs.versions.toml:okhttp = "4.12.0"
gradle/libs.versions.toml:mockwebserver = { group = "com.squareup.okhttp3", name = "mockwebserver", version.ref = "okhttp" }
```

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#329 from dongjoon-hyun/SPARK-53650.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

gradle/libs.versions.toml

@@ -18,7 +18,6 @@
 fabric8 = "7.4.0"
 lombok = "1.18.38"
 operator-sdk = "5.1.2"
-okhttp = "4.12.0"
 dropwizard-metrics = "4.2.30"
 spark = "4.0.1"
 log4j = "2.24.3"
@@ -27,6 +26,7 @@ log4j = "2.24.3"
 junit = "5.13.1"
 jacoco = "0.8.13"
 mockito = "5.18.0"
+okhttp = "4.12.0"
 
 # Build Analysis
 checkstyle = "10.23.1"
@@ -44,7 +44,6 @@ kubernetes-httpclient-vertx = { group = "io.fabric8", name = "kubernetes-httpcli
 kubernetes-server-mock = { group = "io.fabric8", name = "kubernetes-server-mock", version.ref = "fabric8" }
 kube-api-test-client-inject = {group = "io.fabric8", name = "kube-api-test-client-inject", version.ref = "fabric8"}
 crd-generator-apt = { group = "io.fabric8", name = "crd-generator-apt", version.ref = "fabric8" }
-okhttp = { group = "com.squareup.okhttp3", name = "okhttp", version.ref = "okhttp" }
 mockwebserver = { group = "com.squareup.okhttp3", name = "mockwebserver", version.ref = "okhttp" }
 lombok = { group = "org.projectlombok", name = "lombok", version.ref = "lombok" }
 log4j-api = { group = "org.apache.logging.log4j", name = "log4j-api", version.ref = "log4j" }

spark-operator-api/build.gradle

@@ -18,9 +18,7 @@
  */
 dependencies {
   // fabric8
-  implementation(libs.kubernetes.client) {
-    exclude group: 'com.squareup.okhttp3'
-  }
+  implementation(libs.kubernetes.client)
   compileOnly(libs.crd.generator.apt)
   annotationProcessor(libs.crd.generator.apt)
 

spark-operator/build.gradle

@@ -48,8 +48,6 @@ dependencies {
     exclude group: "org.rocksdb"
     exclude group: "org.slf4j"
     exclude group: "org.xerial.snappy"
-    exclude group: 'com.squareup.okhttp3'
-    exclude group: 'com.squareup.okio'
   }
   compileOnly(libs.lombok)
 
@@ -62,11 +60,8 @@ dependencies {
   }
   testImplementation(libs.kubernetes.server.mock) {
     exclude group: 'junit'
-    exclude group: 'com.squareup.okhttp3'
   }
   testImplementation(libs.spark.core) {
-    exclude group: 'com.squareup.okio'
-    exclude group: 'com.squareup.okhttp3'
     exclude group: "org.apache.logging.log4j"
     exclude group: "org.slf4j"
   }