lint should check for duplicate tags

Lint should warn:
- When you use a tag that's "single use only" multiple times (any of the tags that `flatten` flattens to a non-array value)
- When you use a combination of tags that result in something getting overwritten:
- A "kind" tag plus explicit `@kind`
- A "kind" tag with type plus explicit `@type`
- A "kind" tag with name plus explicit `@name` or `@alias`
- Default description plus `@description`