Merge company or person and social profiles in onboarding wizard

[abotteram]

Summary

This PR can be summarized in the following changelog entry:

• Merged company or person and social profiles in onboarding wizard.

Relevant technical choices:

• Added react-select for selecting a WordPress user.

Test instructions

Designs followed: https://github.com/Yoast/design/issues/315

This PR can be tested by following these steps:

• If Updated styled-components to v4+ javascript#184 hasn't been merged yet, make sure to link the mono repo this that PR.

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Quality assurance

• I have tested this code to the best of my abilities
• I have added unittests to verify the code works as intended

Requires Yoast/javascript#184
Requires Yoast/javascript#193

Fixes #12516
Fixes #12519

[afercia]

Not sure why the select in the Settings page is using an aria-label instead of a visible <label> element, which is always preferable.

There's already some visible text that can be used as a <label>:

Visible <label> elements benefit all users, for example they're clickable and allow to easily focus the associated form control.

Also, the current aria-label doesn't match the visible text (whether it's a label or not):
aria-label="Organization or person"

Speech input users will try to voice a command based on the visible text e.g. "Click Choose whether the site represents..." and that won't work.

Overall, I'd recommend to just use the existing visible text as a <label> element.

Also, the visible text and the default option text are pretty much the same and a bit repetitive:

• Choose whether the site represents an organization or a person.
• Choose whether you're an organization or a person

I'd consider to simplify at least the default option.

Can't test the configuration wizard as there's something wrong in my build and I'm getting JS errors.

[afercia]

Re: react-select: worth noting it's not accessible. See #10555 (comment) and https://github.com/Yoast/my-yoast/issues/1530 where it was first noted, as MyYoast is the place where react-select was used first.

Edit: on MyYoast the last usages of react-select were replaced with native styled <select> in https://github.com/Yoast/my-yoast/pull/2213

[moorscode]

Why is there a . in front of this component?

[abotteram]

This is probably a bug in jest-styled-components. We should upgrade to 7.* as soon as it is released (it is currently in beta).

[abotteram]

Merging with consent of @moorscode