Update contracts/exchange-forwarder to 0.5.5

[dorothy-zbornak]

Description

This backports the 0.5.5 update to the exchange-forwarder from the 3.0 branch onto development. This is just a compiler update. There are no meaningful changes to the functionality of the contracts. The PR for that branch is #1732.

Rationale

exchange-forwarder relies on older, pinned dependencies. These pinned dependencies break the build when changes to pervasive packages like base-contract are introduced due to the way dependencies of dependencies are linked in the monorepo. Updating the smart contracts to soldity 0.5.5 removes the requirement for pinned dependencies.

Testing instructions

Types of changes

New feature (non-breaking change which adds functionality)

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.

[coveralls]

Coverage remained the same at 84.764% when pulling 6d2cc56 on feature/contracts/exchange-forwarder/update-to-0.5.5 into d303e9f on development.