Add support for AGP 9.0.0

[dmitriy-sannikov]

Currently, when I'm sync Android project with AGP 9.0.0, fladle plugin 0.19.0 I receive error.

Exception is:
org.gradle.api.ProjectConfigurationException: A problem occurred configuring project ':myProject'.
	
Caused by: java.lang.IllegalArgumentException: Could not find AppExtension in myProject
	at com.osacky.flank.gradle.FladlePluginDelegate.findDebugAndInstrumentationApk(FladlePluginDelegate.kt:193)
	at com.osacky.flank.gradle.FladlePluginDelegate.access$findDebugAndInstrumentationApk(FladlePluginDelegate.kt:16)
	at com.osacky.flank.gradle.FladlePluginDelegate$configureTasks$1$1.execute(FladlePluginDelegate.kt:61)
	at com.osacky.flank.gradle.FladlePluginDelegate$configureTasks$1$1.execute(FladlePluginDelegate.kt:58)
	at org.gradle.api.internal.plugins.DefaultPluginManager$2.execute(DefaultPluginManager.java:261)
	at org.gradle.api.internal.plugins.DefaultPluginManager$2.execute(DefaultPluginManager.java:258)
	at org.gradle.internal.code.DefaultUserCodeApplicationContext$CurrentApplication$1.execute(DefaultUserCodeApplicationContext.java:124)
	at org.gradle.api.internal.DefaultCollectionCallbackActionDecorator$BuildOperationEmittingAction$1.run(DefaultCollectionCallbackActionDecorator.java:109)

I think, this is because of using deprecated API

'class AppExtension : AbstractAppExtension' is deprecated. Replaced by com.android.build.api.dsl.ApplicationExtension and com.android.build.api.dsl.DynamicFeatureExtension.
This class is not used for the public extensions in AGP when android.newDsl=true, which is the default in AGP 9.0, and will be removed in AGP 10.0.

Note: flag android.newDsl=false allows to sync successfully