Execute OpenZeppelin tests in parallel

[bee344]

Currently OZ tests are executed through npx hardhat test. This runs a substrate-node and an eth-rpcin the background, and then runs the tests against it.

The idea is to run several instances of the node at the same time and distribute the workload among them. The problem now is that npx hardhat test already spins up a node instance, and the tests are being ran against that instance. We'd have to run the tests via a runner such as the one used for matter-labs, that selects a subset of tests to run and spins up a node exclusive for those. This could be achieved via adding a network to the hardhat.config file and using that when running npx hardhat test --network NETWORK, but further research is needed to confirm this.

[marshacb]

@bee344 is there a workaround for working with tests that use hardhat-network-helpers such as loadFixture or are these helpers still a blocker for us when running against Kitchensink?

[marshacb]

Adding to backlog due to a number of upstream blockers (test-node implementation and nomicfoundation kitchensink test-network support).