[5.x] Add no default exports custom rule (#10981)

[stacey-gammon]

• Introduce a custom kibana estlint rule for no default exports

Turn it on only at the level of /kibana/src/core_plugins/public/ for
now, just to keep the PR sizes manageable.

• Don't call functions directly on the import

• Create a packages dir and move the custom rule in there

• Remove copied package.json portions, use minimal info necessary

• Have you signed the contributor license agreement?
• Have you followed the contributor guidelines?
• If submitting code, have you included unit tests that cover the changes?
• If submitting code, have you tested and built your code locally prior to submission with npm test && npm run build?
• If submitting code, is your pull request against master? Unless there is a good reason otherwise, we prefer pull requests against master and will backport as needed.

[stacey-gammon]

Failing at:

 ✖ fail: "management scripted fields creating and using Painless date scripted fields should see scripted field value in Discover"
       │        [POST http://localhost:4444/wd/hub/session/1d894cd9-86d6-4b1f-accd-c963d177e8e6/element / {"using":"css selector","value":"visualize-legend"}] no such element: Unable to locate element: {"method":"css selector","selector":"visualize-legend"}
       │         (Session info: chrome=56.0.2924.87)
       │         (Driver info: chromedriver=2.28.455506 (18f6627e265f442aeec9b6661a49fe819aeeea1f),platform=Linux 3.13.0-74-generic x86_64) (WARNING: The server did not provide any stacktrace information)
       │       Command duration or timeout: 10.04 seconds
       │       For documentation on this error, please visit: http://seleniumhq.org/exceptions/no_such_element.html
       │       Build info: version: '3.3.1', revision: '5234b32', time: '2017-03-10 09:04:52 -0800'
       │       System info: host: 'slave-2f8fecba.build.us-west-2a.elasticnet.co', ip: '127.0.1.1', os.name: 'Linux', os.arch: 'amd64', os.version: '3.13.0-74-generic', java.version: '1.8.0_111'
       │       Driver info: org.openqa.selenium.chrome.ChromeDriver
       │       Capabilities [{applicationCacheEnabled=false, rotatable=false, mobileEmulationEnabled=false, networkConnectionEnabled=false, chrome=

and others around painless fields.