Mock validation utility

[archmoj]

Followup of #4762.
Addressing #4733.
Thanks to #5411, now we could node.js for our mock validation 🎉
It is now feasible to run validation tests both locally namely when contributors add new mocks/features to the library, as well as on CircleCI.
While new script does not depend on browserify and jasmine to resolve and load multiple files all at once, it is more robust now and could remove potential side effects of the previous mock_test on parallel runs.

Plus after adding a new mock, it would automatically be tested by this system when there is no need to add its name to the list.

Since we used to run this in noci_test right before publishing (and sometimes fail at final moments), the current setup should help reduce all the noise too.

@plotly/plotly_js

[alexcjohnson]

LGTM! Have you seen this fail on CI? ie just push a branch off this one with a purposely invalid addition to a mock, just to make sure it will properly flag failures for us.

[archmoj]

LGTM! Have you seen this fail on CI? ie just push a branch off this one with a purposely invalid addition to a mock, just to make sure it will properly flag failures for us.

Good call. Tested locally and on the CI.
I also added the option to simply test only the mock(s) needed in 2e8ce24.

[archmoj]

Here the CI failing example:
https://app.circleci.com/pipelines/github/plotly/plotly.js/3826/workflows/b8864a65-0b2a-4382-8f02-0743146be98e/jobs/112705/parallel-runs/0/steps/0-103

[alexcjohnson]

Love it. Especially that we can switch from a whitelist to a blacklist (and hopefully over time cut that list down). 💃