[Backsearch P1] Backsearch misses properties when titles have multiple polygons

[rogup]

Describe the bug

In the backsearch pane, after searching by owner, we display a list of titles. Each title in the INSPIRE dataset can have multiple corresponding polygons. However, due to the way we filter the properties in LeftPaneRelatedProperties.js , we lose some data and only keep track of 1 polygon per title i.e. when we select a related property title, only 1 polygon gets highlighted.

The consequence of this could be that the user misses out on some key info e.g. when researching a landowner, they may own multiple plots of land in the same area but the user will think they just own 1 plot.

To Reproduce Steps to reproduce the behavior:

1. Search for Woodend, West Northamptonshire
2. Enable ownership layer and click on some of the green farmland slightly east of Woodend. The title name is "Oakley Bank Farm, Plumpton and College Farm, Woodend"
3. Check for other properties belonging to the same proprietor (THE PRINCIPAL FELLOWS AND SCHOLARS OF JESUS COLLEGE WITHIN THE CITY AND UNIVERSITY OF OXFORD OF QUEEN ELIZABETH'S FOUNDATION)
4. There is just 1 title in the list. Select this property, but notice that a different polygon has been selected (with same title number)

Expected behaviour Selecting a title in the Backsearch pane selects all of the title's corresponding property polygons.

[rogup]

@lin-d-hop one for you to prioritise

[lin-d-hop]

Added to [Backsearch P1]