extract and reuse ANDROIDX_TEST_VERSION (#26487)

Summary:
This PR is extracts and reuses ANDROIDX_TEST_VERSION, and is part of Gradle script refactoring effort.

## Changelog

[Android] [Changed] - extract and reuse ANDROIDX_TEST_VERSION
Pull Request resolved: https://github.com/facebook/react-native/pull/26487

Differential Revision: D17488766

Pulled By: mdvacca

fbshipit-source-id: f1968ffc403074d78d792eb5cc773cc6366ad2d1

ReactAndroid/build.gradle

@@ -380,9 +380,8 @@ dependencies {
     testImplementation("org.robolectric:robolectric:${ROBOLECTRIC_VERSION}")
 
     androidTestImplementation(fileTree(dir: "src/main/third-party/java/buck-android-support/", include: ["*.jar"]))
-    //TODO: Refactor to extract versions of androidx dependencies
-    androidTestImplementation("androidx.test:runner:1.1.0")
-    androidTestImplementation("androidx.test:rules:1.1.0")
+    androidTestImplementation("androidx.test:runner:${ANDROIDX_TEST_VERSION}")
+    androidTestImplementation("androidx.test:rules:${ANDROIDX_TEST_VERSION}")
     androidTestImplementation("org.mockito:mockito-core:${MOCKITO_CORE_VERSION}")
 }
 

ReactAndroid/gradle.properties

@@ -11,7 +11,7 @@ ROBOLECTRIC_VERSION=3.0
 JUNIT_VERSION=4.12
 FEST_ASSERT_CORE_VERSION=2.0M10
 
-ANDROID_SUPPORT_TEST_VERSION=1.0.2
+ANDROIDX_TEST_VERSION=1.1.0
 FRESCO_VERSION=2.0.0
 OKHTTP_VERSION=3.12.1
 SO_LOADER_VERSION=0.6.0