E2E: Wait for user to be deleted and start clean slate

What does this MR do and why?

Describe in detail what your merge request does and why.

Fixes Group SAML SSO e2e tests by waiting for users to be deleted. This is due to the user deletion happening in batches done by the Users::MigrateRecordsToGhostUserWorker and it takes some time for the deletion to get reflected. See related conversation.

Closes #382024 (closed), #381747 (closed)

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