Clean up usage of fixtures and optimize unit tests

[shahthepro]

Right now, the contracts use hardhat-deploy plugin for deployments. However, we have been wrongly using ethereum-waffle package's createFixtureLoader() method. This essentially means that right now, none of the unit/fork tests are using fixtures at all. Changing them to use hardhat-deploy packages deployments.createFixture fastens the tests by quite a significant time

[naddison36]

I've worked on this today in PR #1745