TabGroup active tab persistence

[haywirephoenix]

Adds the ability for TabGroups to store the active tab since they currently reset on domain reload.

The persistence works by:

• Creating a unique identifier for each tab group based on the object instance ID and property path
• Storing the active tab name in Unity's EditorPrefs using this identifier as the key
• Loading the saved tab selection when the tab group is initialized

Features:

• Persists across domain reloads
• Lightweight and doesn't require additional serialization
• Scoped to the specific Unity project
• Works with TabGroups on multiple objects simultaneously.