Upgrade to support Android 15/API 35

[ochalet-wp]

What

• migrate to Gradle 8 to support running tests and release SDK for Android 15/35
• fix issue with Dokka plugin following to Gradle build - see this link
• fix broken UI test
• upgrade version of Robolectric due to upgrade to Gradle 8 using Java 17
  • we're not using the latest version of Robolectric though because it requires a more recent version of Java
• fix unit test broken when running on Android versions 30 and above. These versions add an additional LengthFilter to EditText when setting up the inputType, which was failing one of our unit test. The testing logic in the unit test has been changed to cater for that. FYI The filter is designed to limit the length of text to 5,000 characters max. The filters added by the SDK will take precedence and will correctly trim the pan, expiry date and cvc to the max length allowed, so we're safe despite this small difference of implementation
• broken UI test was failing due to having omitted to stub the service that deals with assets for card brands. As a consequence requests to retrieve card brand images were failing with 404s and the test was failing

How

• used following guides for upgrading Gradle
  • https://developer.android.com/build/releases/past-releases/agp-8-0-0-release-notes
  • https://docs.gradle.org/current/userguide/upgrading_version_7.html