To make Runtime module optional

[IvanMurzak]

Fact

AI Game Developer supports Unity Editor and Unity Runtime environments.

Problem

• If a user don't want to have Runtime features, it still will be added into the build. That creates unnecessary dependencies in board of a game build, and potential issues for a user.
• AI-Game-Developer-Config.json file is stored under Resources folder that injects the file into a build, which is unnecessary for Editor only use case.

Solution

• To decouple Runtime features into a dedicated package that has Assembly Definition defined correctly to work in Runtime environment.
• To decouple Editor features into a dedicated package that has Assembly Definition defined correctly to work only in Editor environment.
• Do not save AI-Game-Developer-Config.json under Resources folder for Editor only use-case
• Replace AI-Game-Developer-Config.json usage for Runtime use case, add C# API to build and configure UnityMcpPlugin instance differently in runtime