Raise error for external generators or transformers

[CandiedCode]

If duplicate org ids for external transformers or external generators are configured, then throw error instead of swallowing it.

Solves #4562

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[natasha41575]

/ok-to-test
/lgtm

[natasha41575]

Also you can probably ignore the CI failure, #4564 will probably fix it.

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@CandiedCode: This PR has multiple commits, and the default merge method is: merge.
You can request commits to be squashed using the label: tide/merge-method-squash

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[CandiedCode]

/retest

[natasha41575]

/lgtm

[natasha41575]

/retest

[KnVerey]

/label tide/merge-method-squash
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CandiedCode, KnVerey

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