Improve TP Tenant Selection

[shamrickus]

This PR fixes #6427 and arguably #2980. It creates a new directive that can be used to display hierarchical data similar to tenants, and implements it for all tenant fields. It works as a replacement to the select element. I've attached some screenshots at the end.

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Which Traffic Control components are affected by this PR?

• Traffic Portal

What is the best way to verify this PR?

On each of the following pages verify that validation works, and that input actually effects the relevant tenant fields:
Tenants (Add & Edit/View)
Delivery Services (All Types, Add & Edit/View)
User (Add & Edit/View)
User Registration
Origins (Add & Edit/View).

On any page verify that the icons in the drop down are expandable/collapsable, the search box implements a basic fuzzy search, the tooltip works and is position correctly + makes sense, and verify that the input works on all supported TP resolutions.

PR submission checklist

• This PR has tests
• This PR has documentation
• This PR has a CHANGELOG.md entry
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Screenshots

[ocket8888]

I didn't realize that prerequisites file already had mixed indentation. I just looked near the top and saw tabs. It's still a bit messy because of that, but thank you for making it be consistent now.