chore: create ctor overloads for better Java DX

[marandaneto]

💡 Motivation and Context

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

💚 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

📝 Checklist

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

[pauldambra]

nice