Describe the bug
vrcompositor appears to never clear the part of the swapchain image for the right eye, resulting in noticeable flicker from the side of the lens. It's easier to see when looking at the lenses at an angle, but still noticeable when wearing the headset in darker scenes.

To Reproduce
Steps to reproduce the behavior:

1. Launch SteamVR
2. in a darker scene (like the default aurora sky), put the headset on or look at the lenses at an angle
3. observe the flicker/light bleeding from the side of the right lense
4. Alternatively, look at the swapchain image in renderdoc

Expected behavior
There shouldn't be any random data displayed around the image for the right eye, both should be cleared.

System Information (please complete the following information):

• Distribution: Ubuntu 22.04.2 LTS
• SteamVR version: 1.26.7, also happens on the latest Beta (1.27.2)
• Steam client version: 1690583737
• Opted into Steam client beta?: No
• Graphics driver version: Mesa 22.2.5, the same thing happens with Mesa 23.0.4-0ubuntu1~22.04.1 (LLVM 15.0.7)
• Gist for SteamVR System Information: https://gist.github.com/Coreforge/7c695d44e222d0520f2b61542c80df9b

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
Renderdoc capture: https://drive.google.com/file/d/15hgEKLMgdocxYvmQ-imJfBLgL82FFRh0/view?usp=sharing
EID 131 (left eye -> Scene -> Scene / Lens Distortion -> vkCmdBeginRenderPass) clears the area for the left eye in vkCmdBeginRenderPass
EID 277 (right eye -> Scene -> Scene / Lens Distortion -> vkCmdBeginRenderPass) does not clear the area for the right eye, resulting in random data being left in the final image (clearValueCount is 0 in the VkRenderPassBeginInfo)

Note: Commenters who are also experiencing this issue are encouraged to include the "System Information" section in their replies.