galley-types: remove all re-exports

[smatting]

https://wearezeta.atlassian.net/browse/BE-567

Checklist

• The PR Title explains the impact of the change.
• The PR description provides context as to why the change should occur and what the code contributes to that effect. This could also be a link to a JIRA ticket or a Github issue, if there is one.
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[smatting]

There are clashing names, e.g. Event exists in Wire.API.Event.Team and Wire.API.Event.Conversation. There is some risk that I've made an error and mixed them up at places where type checking ends: at serialization/deserialization. However I hope that API tests would catch that.

[elland]

Nice!