Standardize MediaRoutingDemo dependencies

Replace pre-built dependencies with source dependencies where
applicable, and with project-defined prebuilts where not
applicable.

The concrete issue that this CL fixes is testing U features
in the internal branch. Where BuildCompat.isAtLeastU() would
run an outdated implementation that was failing on the
tip-of-branch, which is no longer pre-release.

Bug: 280034226
Test: Gradle sync and build, and manual testing of the app.
Change-Id: I8b6dd268b697f0d0bf40e85a161c756b5adabee7

Author: AquilesCanta

samples/MediaRoutingDemo/build.gradle

@@ -4,14 +4,14 @@ plugins {
 }
 
 dependencies {
-    implementation("androidx.appcompat:appcompat:1.6.0")
+    implementation(project(":appcompat:appcompat"))
     implementation(project(":mediarouter:mediarouter"))
-    implementation("androidx.recyclerview:recyclerview:1.2.1")
-    implementation("androidx.concurrent:concurrent-futures:1.1.0")
-    implementation(libs.material)
+    implementation(project(":recyclerview:recyclerview"))
+    implementation(project(":concurrent:concurrent-futures"))
 
-    implementation ("androidx.multidex:multidex:2.0.1")
-    implementation("com.google.guava:guava:31.1-android")
+    implementation(libs.material)
+    implementation(libs.multidex)
+    implementation(libs.guava)
 }
 
 android {