Use Mockito Java agent for mock instrumentation (#2275)

This change fixes the following warning during tests:

    Mockito is currently self-attaching to enable the inline-mock-maker. This will no longer work in future releases of the JDK. Please add Mockito as an agent to your build as described in Mockito's documentation: https://javadoc.io/doc/org.mockito/mockito-core/latest/org.mockito/org/mockito/Mockito.html#0.3
    WARNING: A Java agent has been loaded dynamically (.../byte-buddy-agent-1.17.5.jar)
    WARNING: If a serviceability tool is in use, please run with -XX:+EnableDynamicAgentLoading to hide this warning
    WARNING: If a serviceability tool is not in use, please run with -Djdk.instrument.traceUsage for more information
    WARNING: Dynamic loading of agents will be disallowed by default in a future release

Author: adutra

build-logic/src/main/kotlin/polaris-java.gradle.kts

@@ -140,6 +140,8 @@ testing {
   }
 }
 
+val mockitoAgent = configurations.create("mockitoAgent")
+
 dependencies {
   val libs = versionCatalogs.named("libs")
   testFixturesImplementation(
@@ -155,18 +157,24 @@ dependencies {
       GradleException("assertj-core not declared in libs.versions.toml")
     }
   )
-  testFixturesImplementation(
+  val mockitoCoreLib =
     libs.findLibrary("mockito-core").orElseThrow {
       GradleException("mockito-core not declared in libs.versions.toml")
     }
-  )
+
+  testFixturesImplementation(mockitoCoreLib)
+
+  mockitoAgent(mockitoCoreLib) { isTransitive = false }
 }
 
 tasks.withType<Test>().configureEach {
   systemProperty("file.encoding", "UTF-8")
   systemProperty("user.language", "en")
   systemProperty("user.country", "US")
   systemProperty("user.variant", "")
+  jvmArgumentProviders.add(
+    CommandLineArgumentProvider { listOf("-javaagent:${mockitoAgent.asPath}") }
+  )
 }
 
 tasks.withType<Jar>().configureEach {