Fix hardhat "uninitialized provider" issue

[MathisGD]

When using the latest version of hardhat and dependencies, yarn test is failing with this:

Error HH21: You tried to access an uninitialized provider. To initialize the provider, make sure you first call `.init()` or any method that hits a node like request, send or sendAsync.

For more info go to https://hardhat.org/HH21 or run Hardhat with --show-stack-traces
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

It is fixed by using a modified yarn.lock file, but we should find a fix to use the latest version of hardhat.

Working yarn file: yarn.lock.txt
Diff: diff.txt

[Rubilmax]

I am aware of this and didn't find any workaround for now. Let's just use 2.15.

[MathisGD]

@MerlinEgalite is proposing a temporary workaround in #35

[MathisGD]

Not closing this, as it would be better to find a fix and use the last version of HH

[MathisGD]

NB: v2.16.0 of hardhat touches to providers so I'm not surprised.