CTRT edits to Labels documentation

What does this MR do?

Edit Labels doc to follow CTRT.

Reading level:

Before	After
7.90	6.18

Visual comparison (before review):

Before	After
	Clean up intro concepts a bit.
	Clean up intro and steps, use a list for quick actions.
	Delete topic and include permission info in each task topic. This also allowed one fewer level of other headings.
	✂ Cut and incorporate into task topics that cover both projects and groups.
	✂ Cut and incorporate into task topics that cover both projects and groups.
✂	Task topics continued.
✂
✂
	Make into a task + fix tier.
✂
✂
	It's still long but I verified prerequisites and cleaned up steps + fixed for style.
	Added steps and prerequisite.
	Small intro clean-up + moved example to examples + added new video link
	Revise note for style
	Renamed to "examples" and streamlined + added example from intro + embedded YT video (because from official channel)
	Used lists
	Made into a task + deleted image
	Deleted an image and moved background info to sorting_issue_lists.md and crosslink
Troubleshooting	No change

Related issues

Part of technical-writing#531 (closed)

Author's checklist

• Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
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  • Style Guide.
• Ensure that the product tier badge is added to topic's h1.
• Request a review based on:
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  • The associated Technical Writer.

If you are only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Review checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
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  • Ensure the appropriate labels are added to this MR.
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    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
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