Review, Refactor, and Improve Token Swap implementation

[sentientforest]

An old token swap implementation was migrated from an internal codebase to the public sdk for broader consumption in pull request #468.

The scope of this issue is to take the migrated code, finish updating it to use more modern methods provided by the v2.x SDK, review it for potential security and refactoring improvements, and look for opportunities to share code with the recently drafted Token Sale feature (related issue: #443).

Open feedback left on the merged pull request #468 should be addressed in addition to the above higher level goals:

• fix, resolve, or delete old todo comments
• standardize use of UserAlias, await resolveUserAlias(), UserAlias in swap function params
• error handling updates - this code was written long before ChainErrors were standardized and provided in the SDK and there are several places where errors can be handling differently