Move server service level objectives to servers.json

[nathannfan]

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This change is 

[balajikris]

Hey @nathannfan - so all commits to this PR are purely moving stuff from one spec to another? No other additions/deletions expected?

[nathannfan]

@balajikris yep, just doing this to rework the categories we're generating in docs.microsoft.com. I did have to copy SubResource to servers.json as a dependency, but nothing new.

[balajikris]

For existing warns/errors, there is a open workitem that we're tracking. This PR doesn't create any new violations. I've reviewed the changes and I'm okay with it. Merging in as is.

[nathannfan]

Thanks, @balajikris!

[AutorestCI]

No modification for NodeJS

[AutorestCI]

Azure/azure-sdk-for-ruby#780

[AutorestCI]

Azure/azure-sdk-for-python#1177