Replace references to android.support.test with androidx.test.

The Android Test Support Library is being renamed to AndroidX Test, with its root java namespace changing from android.support.test to androidx.test.
And code location changing from tp/android/android_test_support to tp/android/androidx_test.

More information: []

TAP global presubmit: []

BUG:
79205333

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=202796842

library/core/build.gradle

@@ -28,7 +28,7 @@ android {
         targetSdkVersion project.ext.targetSdkVersion
         consumerProguardFiles 'proguard-rules.txt'
 
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
 
         // The following argument makes the Android Test Orchestrator run its
         // "pm clear" command after each test invocation. This command ensures

library/core/src/androidTest/java/com/google/android/exoplayer2/upstream/ContentDataSourceTest.java

@@ -28,8 +28,8 @@ import android.os.Bundle;
 import android.os.ParcelFileDescriptor;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-import android.support.test.InstrumentationRegistry;
-import android.support.test.runner.AndroidJUnit4;
+import androidx.test.InstrumentationRegistry;
+import androidx.test.runner.AndroidJUnit4;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.testutil.TestUtil;
 import java.io.FileNotFoundException;

library/core/src/androidTest/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndexTest.java

@@ -19,9 +19,9 @@ import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth.assertWithMessage;
 
 import android.net.Uri;
-import android.support.test.InstrumentationRegistry;
-import android.support.test.runner.AndroidJUnit4;
 import android.util.SparseArray;
+import androidx.test.InstrumentationRegistry;
+import androidx.test.runner.AndroidJUnit4;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.util.Util;
 import java.io.File;

library/core/src/androidTest/java/com/google/android/exoplayer2/upstream/cache/SimpleCacheSpanTest.java

@@ -18,8 +18,8 @@ package com.google.android.exoplayer2.upstream.cache;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth.assertWithMessage;
 
-import android.support.test.InstrumentationRegistry;
-import android.support.test.runner.AndroidJUnit4;
+import androidx.test.InstrumentationRegistry;
+import androidx.test.runner.AndroidJUnit4;
 import com.google.android.exoplayer2.util.Util;
 import java.io.File;
 import java.io.FileOutputStream;