update agp, kotlin, appcompat and exoplayer

* agp 4.2.2 -> 7.0.0
* kotlin 1.5.20 -> 1.5.21
* appcompat 1.3.0 -> 1.2.1
* exoplayer 1.14.1 -> 1.14.2

build.gradle

@@ -1,12 +1,12 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 buildscript {
-    ext.kotlin_version = "1.5.20"
+    ext.kotlin_version = "1.5.21"
     repositories {
         google()
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.2.2'
+        classpath 'com.android.tools.build:gradle:7.0.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong