Fallback to getting collectible contract information from the contract itself.

Currently the controller is getting collectible contract name and symbol information from the contract itself, but all other information is retrieved from OpenSea. As a fallback, metamask could pull information directly from the contract if OpenSea doesn't have the data. This could use the OpenSea standard here for "contractURI": https://docs.opensea.io/docs/contract-level-metadata

A big motivation for this is currently only projects on the 3 chains supported by OpenSea can have icons for their NFT collections in metamask mobile. This would provide a mechanism for projects that aren't on a chain support by OpenSea to specify an image icon for their NFT collections.

Start by reading the controller's existing collectible contract name and symbol handling, then review the OpenSea contractURI standard linked in the issue. Trace how the remaining collection metadata is retrieved from OpenSea and define the fallback path for missing data, including collection images; done means supported contracts can provide metadata when OpenSea has none.

Written by the indexing model from the issue text.