fix(ui) Fix duplicate schema field rendering with siblings

[chriscollins3456]

We had an issue reported by several users where scrolling on their schema caused the same field to be repeated and take over the whole schema. This was happening because the key of one (or more) the schema rows had a duplicate, causing bad rendering issues and duplicating the same rows.

This could happen when two siblings had different schemas. If one of the schemas had an extra row or two inserted in the middle, the two schemas would be merged by index and therefore we would produce duplicate fields, causing duplicate rows, breaking the schema renderer.

This fixes the issue by merging based on the fieldPath instead, so now we get a combined schema of the siblings with unique field paths, preventing duplicated.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[gabe-lyons]

lgtm!