fix: add gax testlib to java-bigquery

This includes the necessary build-time initialization flags (see [properties file](https://github.com/googleapis/sdk-platform-java/blob/1eb107d1c09d8a2182fe0f550bf23e3ca3ac414f/gax-java/gax/src/test/resources/META-INF/native-image/com.google.api/gax/native-image.properties)

Author: diegomarquezp

google-cloud-bigquery/pom.xml

@@ -157,6 +157,12 @@
     </dependency>
 
     <!-- Test dependencies -->
+	<dependency>
+      <groupId>com.google.api</groupId>
+      <artifactId>gax</artifactId>
+      <classifier>testlib</classifier>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-datacatalog</artifactId>