Refactor TokenAdjacency and TokenAdjacencyBuilder [TKR-324]

[kyu-c]

Description

• Factor out interface TokenAdjacency and its utility functions (builder, and getIntermedidateTokens into classes.
• Added tests!
• The new TokenAdjacencyBuilder ensures that token addresses are lower-cased so that the user of TokenAdjacency does not need to worry about sanitizing token addresses.
• Add addBidirectional and addCompleteSubgraph in TokenAdjacencyBuilder
  • In the vast majority of the case, liquidity is bi-directional
  • addCompleteSubgraph will be useful for a case where a set of tokens can be swapped among each other (the major use case would be Synthetix atomic swap).

Testing instructions

• Did local testing with pairs requiring multihiop (cvxCRV, wstETH)

Types of changes

Checklist:

• Prefix PR title with [WIP] if necessary.
• Add tests to cover changes as needed.
• Update documentation as needed.
• Add new entries to the relevant CHANGELOG.jsons. (will be done before this PR is merged).