How to reproduce:
1. Open up URP's GraphicsTestProject_Foundation
2. Open scene: 012_PBS_EnvironmentBRDF_Spheres
3. Enable the Frame Debugger and select one of the Clear events and the surrounding events in the Frame Debugger Tree
4. Notice that a clear event is disappearing and reappearing
5. Also notice that the RenderTarget name index keep increasing (TempBuffer <num>)

Reproducible with: 2021.2.0a19, 2021.2.0b2, 2022.1.0a2
Not reproducible with: 2019.4.29f1, 2020.3.13f1, 2021.1.14f1, 2021.2.0a18

Notes:
1. Tested with URP and Built-In
2. Graphics APIs tested: Metal(OSX), OpenGLCore(OSX and Windows), D3D11(Windows), D3D12(Windows), Vulkan(Windows)
3. The issue happens both in playmode and non-playmode. The flickering happens a lot more in non-playmode.