chore: create ctor overloads for better Java DX

[marandaneto]

:bulb: Motivation and Context

https://posthog.com/questions/setup-using-android-java-project

:green_heart: How did you test it?

// PostHogAndroidConfig config = new PostHogAndroidConfig("key"); // PostHogAndroidConfig config = new PostHogAndroidConfig("key", "host"); // PostHogAndroidConfig config = new PostHogAndroidConfig("key", "host", true); ... etc using a Java file

:pencil: Checklist

• [X] I reviewed the submitted code.
• [ ] I added tests to verify the changes.
• [ ] I updated the docs if needed.
• [X] No breaking change or entry added to the changelog.