How to reproduce:
1. Open the attached "1259860 repro" project
2. Select "ProblematicPrefab" Prefab from the Assets folder

Expected result: OnValidate() method isn't called every frame when the "TestScript" attempts to rename a Prefab
Actual result: OnValidate() method is called every frame as seen in the Console window

Reproducible with: 2018.4.24f1, 2019.4.3f1, 2020.1.0a22
Not reproducible with: 2020.1.0a23, 2020.1.0b14, 2020.2.0a16

Notes:
-On 2018.4 and 2019.4 streams "Assertion failed on expression 'gForceReimports->empty()'" error is thrown after deselecting the Prefab
-This issue only reproduces when the Prefab is selected in the Project window since it can't be renamed there
-On the affected versions, the OnValidate() method is called an infinite amount of times while on the not affected versions the OnValidate() method is only called twice
-If the 7th line of the "TestScript.cs" is commented out (name = "TestName";), the issue usually still reproduces until the Editor is restarted