validate `caps` and `appium_lib`

[KazuCocoa]

This is a

• Bug report
• Question
• Freature Request

Summary

Current configuration format is:

{
  caps: { ... }, # <= send to server as capability
  appium_lib: { ... } # <= client side
}

Sometimes I see the wrong format like:

{ caps: { ...., appium_lib: { ...} }  }

If a warning is raised on the debug log, it looks more helpful.

Environment

• ruby_lib version: 9.7.1