Extract common sample gradle config into shared file

[zach-klippenstein]

If you think this will be the same for all apps you could just extract it into a separate .gradle file and apply to demo apps.

Something like:

./buildscript/configure-sample-app.gradle

apply plugin: 'com.android.application'

android {
  defaultConfig {
    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
  }

  testOptions {
    animationsDisabled = true
  }
}

dependencies {
  androidTestImplementation deps.test.androidx.espresso.core
  androidTestImplementation deps.test.androidx.junitExt
  androidTestImplementation deps.test.androidx.uiautomator
}

and just apply that at the top:

apply from: rootProject.file('.buildscript/configure-sample-app.gradle')
apply plugin: 'kotlin-android'

android rootProject.ext.defaultAndroidConfig

android {
  defaultConfig {
......

Originally posted by @tehras in #966

[wugeorgeq]

Is this still a good first issue if I want to start contributing? :)