Rework /deliveryservice_server/:dsid/:serverid

[mhoppa]

What does this PR (Pull Request) do?

• This PR is not related to any Issue

Deprecates DELETE /deliveryservice_server/:dsid/:serverid and makes a new endpoint DELETE /deliveryserviceserver/:dsid/:serverid in 2.0 that replaces the functionality

Which Traffic Control components are affected by this PR?

• Documentation
• Traffic Ops

What is the best way to verify this PR?

Run traffic ops and make sure you can not hit the endpoint DELETE /deliveryservice_server/:dsid/:serverid in API 2.0 and when performing a DELETE on it in 1.x you receive a deprecation message back in the returned alerts. .

Make requests to DELETE /deliveryserviceserver/:dsid/:serverid and ensure it works.

If this is a bug fix, what versions of Traffic Control are affected?

The following criteria are ALL met by this PR

• This PR includes tests OR I have explained why tests are unnecessary
• This PR includes documentation OR I have explained why documentation is unnecessary
• This PR includes an update to CHANGELOG.md OR such an update is not necessary
• This PR includes any and all required license headers
• This PR ensures that database migration sequence is correct OR this PR does not include a database migration
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Additional Information

[shamrickus]

LGTM

• TO unit/integration tests pass
• No go fmt issues
• deliveryservice_server/... is gone in 2.0 and deprecated in 1.1
• deliveryservicesserver/... works the same as the old 1.1 version
• No docs issues
• All references in ORT/client/TP updated
• TP tests pass