Revert `merge_requests/47323` and `merge_requests/42877`

What does this MR do?

This MR solves the issue described at: #281183 (comment 449569237)

Problem description:

However the installation instructions for Docker and Kubernetes currently only displays a link to the docs page and blank content for the Register Runner - Method panel.
2020-11-13: Also, Viktor Nagy pointed out the following in the linked video:

- The initial load time for the pop up is slow.
- The panel content should reflect the tab that the user has selected.
- The copy selection for the install instructions does not work.

There's some other broken behaviour which I suspect would still be present in the non-pop-up version and we should probably prioritize improving that:

First,

1. Open the dialog. Choose `macOS`. Leave the CPU alone for now. Close the dialog.
1. Without refreshing the page, open the pop-up again.
1. `Linux` is now selected as the OS but the `macOS` instructions are still present.

Second,

I can't reproduce this myself because I don't have a dev environment set up at the moment but I'm hearing the results are even more strange when trying to add a runner at the group level.

This MR is a revert of two MRs:

• !47323 (merged)
• !42877 (merged)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team