Add ability to set Token Images, Portraits, and Handouts from addon assets (include copy/create token)

[cwisniew]

Identify the Bug or Feature request

Resolves #4183

Description of the Change

Added a utility class to resolve assets from different locations and the ability to retrieve the asset key from add ons.
Modified the following macro functions to use this new resolver

• createToken()
• copyToken()
• setTokenImage()
• setTokenPortrait()
• setTokenHandout()

Possible Drawbacks

Should be none

Documentation Notes

The following macro functions can now use lib:// URIs for assets

• createToken()
• copyToken()
• setTokenImage()
• setTokenPortrait()
• setTokenHandout()

the URIs already work with tags so can be used in dialog, frame, chat, and macro buttons. This means they should hopefully be useable everywhere now.

Release Notes

• Added ability to specify assets for macro functions from lib:// URIs

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This change is