fix(android): Integer conversion of compileSdk/minSdk/targetSdk

[saschpe]

Gradle properties are always parsed as strings from gradle.properties. While Gradle Groovy can utilize the ext Gradle plugin directly, Gradle Kotlin DSL projects have to specify properties in gradle.properties. Convert those to integers as required by Android Gradle Plugin (AGP). This won't affect projects that still use Gradle Groovy.

Resolves #5194

[saschpe]

I would be nice if someone could provide some feedback for this fix. Thanks.

[saschpe]

I would appreciate if this could be looked at. At the moment it is not possible to put this into one's gradle.properties, simply because those are interpreted as strings:

compileSdkVersion=33
minSdkVersion=23
targetSdkVersion=33

The same change for capacitor-plugins