feat: add additional CAIP-19 types and parsing functions to align with proposal

[erwolff]

Added full support for CAIP-19 Asset IDs including the necessary regex, structs, and parsing functions.

A few notes:

• While the regex of a chain namespace is technically the same as an asset namespace, the official proposal makes a clear distinction between the two, and so it's within the spirit of the spec to break these out into separate properties. The same cannot be said for a chain reference vs asset reference: these require different regex for validation.
• Previously, CaipAssetId required a tokenId (/${string}) to be present. This has been changed to allow for tokenId to be optional (as dictated by the official proposal) in both the type and its corresponding regex string
• For completeness, toCaipAccountId and parseCaipAssetId functions were added