Only allow removal of API if it was deprecated

[agi90]

We need a new mode in api-lint to enforce that only APIs that have been deprecated for a certain amount of time can be removed.

[agi90]

Also we need a way to override that for the inevitable times where we need to break compat and there's no way to avoid it.

[agi90]

Also (this might be a separate issue) a way for api-lint to nag about APIs that have not been removed but should have been removed. E.g. remove APIs after 3 releases that have been deprecated.