How to reproduce:
1. Open the attached project
2. In the Hierarchy search for "test" and select all of the objects
3. In the object Inspector interact with the array script (fold unfold array fields, add components, etc)
4. Observe the poor performance

Expected result: the Inspector is fully functional and performant even when multi selecting objects
Actual result: the Inspector is slow when multi selecting objects with reorderablelist arrays

Reproducible in:2021.1.0a9, 2020.2.0f1, 2020.2.0a13
Not reproducible in: 2020.2.0a12, 2020.1.17f1, 2019.4.16f1, 2018.4.30f1, 2017.4.40f1 (these versions do not use the reorderable list control by default and thus don't suffer the performance downgrade)