Add command to get list of tests in json format

[Ameterezu]

Motivation

Added the ability to get a list of tests in json format.
Filtering of tests through grep and fgrep is supported.
Export of the list to a file is supported.
New functionality will allow to control the launch of tests remotely by it's name.

Command:
npx codeceptjs list-of-tests --grep "My test name" --file

Type of change

• 🚀 New functionality

Checklist:

• Tests have been added
• Documentation has been added (Run npm run docs)
• Lint checking (Run npm run lint)
• Local tests are passed (Run npm test)

[DavertMik]

Thanks for the PR!
However, I don't think it should be part of CodeceptJS main package. It adds an independent command, so I think it can be published as a standalone package on npm and added to the list of community driven packages https://github.com/codeceptjs/CodeceptJS/wiki/Community-Helpers-&-Plugins

Not an issue with the code itself. But when it is used to solve some very specific issue I prefer to not pull this change into the main codebase. Anyway, this is good to have it as a different command

[lyubenkov]

@DavertMik Thanks for your detailed feedback, but I still don't understand why json format can't be a part of the main package.
Codeceptjs has in-build ability to export list of tests in a plain text format (dry-run). But such format can't be processed easily afterwards. Isn't it better to support json out of the box?