Add support for custom font asset path in config

[iujames]

This is to support custom font loading in React Native Expo projects, on Android. The new config option for fontAssetPath will allow specifying something other than the default (/assets/fonts), since Expo apps put custom fonts in the /assets root.

• update the Debugger list of fonts to look in both the default /assets/fonts and any custom path provided
• update the runtime styling for text to look for custom fonts in both the default and any custom path

The majority of the changes here are propagating a new CompositionLocal for AppcuesConfig down through the spots that eventually need it for text styling.

[shortcut-integration[bot]]

This pull request has been linked to Shortcut Story #57692: Support a custom font path.