cli: Allow passing arguments to an underlying script

[sushi-shi]

Sometimes it is desirable to run only specific test cases. For this it is required to let the underlying script know which tests should be run.
For example, given this Anchor.toml

[scripts]
mocha = "yarn run ts-mocha -t 1000000"

It is desirable to be able to run:

$ anchor run mocha -- ./tests/one-specific-test.ts

[armaniferrante]

Thank you!