TP: sorts the results of GET /tenants to represent the hierarchy

[mitchell852]

What does this PR do?

Fixes #3159

Which TC components are affected by this PR?

• Documentation
• Grove
• Traffic Analytics
• Traffic Monitor
• Traffic Ops
• Traffic Ops ORT
• Traffic Portal
• Traffic Router
• Traffic Stats
• Traffic Vault
• Other _________

What is the best way to verify this PR?

1. Launch TP
2. Navigate to https://tp.domain.com/#!/tenants
3. Verify that the list of tenants represents the hierarchy. I.e.

root
root.1
root.1.1
root.1.2
root.2
root.2.1
root.2.2

Also edit a tenant, delivery service, origin or user and ensure that the Tenant dropdown is ordered properly

Check all that apply

• This PR includes tests
• This PR includes documentation updates
• This PR includes an update to CHANGELOG.md
• This PR includes all required license headers
• This PR includes a database migration (ensure that migration sequence is correct)
• This PR fixes a serious security flaw. Read more: www.apache.org/security

[asfgit]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/trafficcontrol-PR/2990/
Test PASSed.

[asfgit]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/trafficcontrol-PR/2992/
Test PASSed.

[dangogh]

tested in cdn-in-a-box:

• added new tenant 2 levels down
• edit and new: user, tenant, deliveryservice, origin all display the hierarchy properly