Create Token Cache Provider

[marstr]

If an MSAL Token cache has been serialized into a well-known location, and the current user has access to it, this Token Provider should be able to reach-into that cache and get a token with the appropriate scopes for a user.

[rayluo]

Closing old issues. This one seemed to be a behavior which MSAL EX supported since early days, anyway. In fact, app developers can and must specify a location. If such a location is "well-known" by several apps, those apps would be able to reach into that location/cache and get the content from it.