[SDK Refactor] New top level package `testing-kit`

[dasanra]

Context / issue

We have code repetition for testing. Between the protocol-kit, api-kit, and relay-kit, we share some common utilities that can be extracted into a shared package

Proposed solution

Create a new testing-kit package. This package should include:

• hardhat configuration
• Contract deployments
• Common utils

This package allows us to remove code from the repository and concentrate the testing utilities in one place. This approach helps avoid errors and makes it easier to kickstart new packages.

Additional context

Research document