fix: Updating to Gradle 8

[theproducer]

This PR brings Background Runner inline with other Capacitor 5 plugins.

[jcesarmobile]

I've sent a similar PR that just updates the capacitor-plugin folder using the migrate helper

#18

We can use yours since it also updates the library, but there are some missing or incorrect things.
In all other plugins we used gradle plugin 8.0.0 instead of 8.0.2, I don't think it would be bad to use a different version, but probably for consistency should use the same.
The gradle wrapper should be 8.0.2-all instead of 8.0-bin as 8.0 and 8.0.1 had some bugs.
Also the gradle files should be updated, you can run ./gradlew wrapper --distribution-type all --gradle-version 8.0.2 --warning-mode all (sometimes need to be run twice for the files to update)

Remove android.enableJetifier=true from the gradle.properties files