Modernize plugin

[TWiStErRob]

• Remove Gradle 4.x support (implies AGP 3.1 and 3.2 support removed) #377
• Remove Gradle 5.x and 6.x support (implies AGP 3.x and 4.x support removed) #434
• Remove most of AGP pre-7.x code #435
• Clean up outdated language dependencies (Java 8, Kotlin 1.3) #439
• remove old version support (lots of ifs, matrix)
• Review .provider { } usages #454
• Remove instant support #375 -> Remove all mentions of instant app in AGP #449
• bump Mockito to 5.x Update mockito monorepo from 4.11.0 to 5.0.0 (major v5) (major) #365 -> Update mockito monorepo from 4.11.0 to 5.2.0 (major v5) (major) #447
• Update dependency org.junit-pioneer:junit-pioneer from 1.9.1 to 2.0.0 (major v2) - retry #398 -> Update dependency org.junit-pioneer:junit-pioneer from 1.9.1 to 2.0.0 (major v2) #446
• AndroidManifest.xml's package is deprecated -> android.namespace #233 -> Fix #233: Migrate AndroidManifest.xml to namespace #450
  use namespaces in AGP tests (when was namespaces introduced?)

  > Task :processDebugMainManifest
  package="net.twisterrob.gradle.test_app" found in source AndroidManifest.xml: C:\Users\TWiStEr\AppData\Local\Temp\junit10040231846123388609\src\main\AndroidManifest.xml.
  Setting the namespace via a source AndroidManifest.xml's package attribute is deprecated.
  Please instead set the namespace (or testNamespace) in the module's build.gradle file, as described here: https://developer.android.com/studio/build/configure-app-module#set-namespace
  This migration can be done automatically using the AGP Upgrade Assistant, please refer to https://developer.android.com/studio/build/agp-upgrade-assistant for more information.
  

• Modernize testing frameworks and test fixtures #452 replace apply plugin: with plugins {}
• Modernize testing frameworks and test fixtures #452 replace buildscript with plugins in fixtures
• Modernize testing frameworks and test fixtures #452 replace lintOptions and compileSdkVersion with newer APIs
• review AGP lifecycle hack (removed in Remove most of AGP pre-7.x code #435)
• net.twisterrob.gradle.build.hackKotlinMetadata (gone)
• Rewrite versioned APK file renaming #456
• Modernize testing frameworks and test fixtures #452 Replace !!.outcome with .assert* calls
• Use .kts in tests #455