Add LimitOffsetPagingSource unit test

Add unit test that blocks Room's InvalidationTracker's invalidation
signal to ensure that LimitOffsetPagingSource is using
refreshVersionsSync properly to check for tables invalidation.

Moved some test utils to general androidx test utils.

Bug: 193745836
Fixes: 193745836
Test: ./gradlew room:room-paging:cC
Test: ./gradlew :room:integration-tests:room-testapp-kotlin:cC
Change-Id: I689481d746c588c1cf25eeb4b9ff039eff55b1f9
diff --git a/testutils/testutils-common/build.gradle b/testutils/testutils-common/build.gradle
index bea9428..dccc2a9 100644
--- a/testutils/testutils-common/build.gradle
+++ b/testutils/testutils-common/build.gradle
@@ -1,3 +1,5 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
 /*
  * Copyright 2018 The Android Open Source Project
  *
@@ -21,4 +23,12 @@
 
 dependencies {
     implementation(libs.kotlinStdlib)
+    implementation(libs.kotlinCoroutinesAndroid)
+}
+
+// Allow usage of Kotlin's @OptIn.
+tasks.withType(KotlinCompile).configureEach {
+    kotlinOptions {
+        freeCompilerArgs += ["-Xopt-in=kotlin.RequiresOptIn"]
+    }
 }