[FE] DevOps Report: Segment modal

• Create the segment modal and show top-level groups only in first iteration.
• Requesting data and submitting changes, see here: #262395 (comment 433755122)
• When the segment has been created, use a toast like this to indicate success or error.
• Use a toast with type success for created and type error for errors!

For more information see the discussion here: #235421 (comment 433747317)

Related to: #235421 (closed)

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