feat: pre-fill existing tags for insights, actions, event definitions, and property definitions

[pauldambra]

Problem

closes #10678

There are several pages where you can add tags to an item. But we only suggest existing tags on one of them.

Changes

Suggest tags on insight, action, event definitions, and property definition pages

Adds an API to event definitions and property definitions to allow this. There's no pagination but there are (at least for now) very few tags on these types.

property definitions

### event definitions

insights

actions

How did you test this code?

added developer tests and checked in the UI locally

[mariusandra]

Hmm.. I think tags should be global. That means, if you add a tag "marketing" for an insight, the same tag should be available when you tag actions. There's a lot of code duplication here to prevent that from being a thing.

Also, to avoid refactoring this later, I think we should use the taxonomic filter to select tags, giving us autocompletion and pagination virtually for free.

[pauldambra]

I think tags should be global.

fair

we should use the taxonomic filter

Oh, I hate changing the taxonomic filter 🤣 . I think I'll split this into two steps ✂️

[posthog-bot]

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[pauldambra]

Tags are now project "global"

[mariusandra]

I could nit on a thing here or there, but I won't 😅. Looks good to me! 👍