This commit adds a top level assert.register() API to the test
runner. This function allows users to define their own custom
assertion functions on the TestContext.
Fixes: https://github.com/nodejs/node/issues/52033
PR-URL: https://github.com/nodejs/node/pull/56434
Reviewed-By: Jacob Smith <jacob@frende.me>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Pietro Marchini <pietro.marchini94@gmail.com>
