Integration testing with Node Test Runner

[kanej]

Add integration testing support to Hardhat v3 based on Node Test Runner.

Node Test Runner support will be implemented as a separate package and plugin. It will add a hardhat test task that will initialize the hre and then execute the test suites, injecting the HRE into the context.

Full details can be find in the design doc.

TODO

• Add a new @ignored/hardhat-node-test-runner package under ./v-next
• Implement as a plugin task shim code similar to v2 mocha, that runs the designated test folder js/ts files as tests in Node test runner. Before the tests are run the HRE should be initialized and injected into the context.
• Include the Hardhat custom test reporter in the default execution
• Add @ignored/hardhat-node-test-runner to the example project and add some basic integration tests confirming that testing works and that the hre is being initialized
• Add support for --only to the npx hardhat test command

Out of Scope

• Coverage
• Gas reporting
• Parallel test execution
• Support for console.log in tests