DOCS-3944: Restructure motion docs

[JessamyT]

Todo:

• Remove most of content from "Move an arm" landing page and make it a very brief overview
• Add full code to arm w/motion page after testing
• Add more details about figuring out frames to configure
• Delete frame tab content
• Fix links
• Potentially delete the old motion tutorials

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[JessamyT]

Will delete; just keeping for copy-paste ease reasons for now

[JessamyT]

Will delete; just keeping for copy-paste ease reasons for now

[viambot]

It looks like the following files may have been renamed. Please ensure you set all needed aliases:
rename docs/operate/mobility/{move-arm.md => move-arm/_index.md} (99%)