Steps to reproduce:
# Create a new project
# Create a new material in the Assets/ folder in the Project window
# Select the material and navigate to the Inspector (make sure visual preview is brought up)
# In the preview section, click on the "Shape" button next to the "Play" button to change the material preview model

Expected result: the material is previewed on selected 3D models

Actual result: the 3D model does not change

Reproduces on: 2023.3.0a8 (trunk)

Does not reproduce on: 2023.1.3f1
h2. Preliminary investigation results

There are multiple instances of MaterialEditor that get created and the button event seem to be forwarded to a leaked instance.
* This bug doesn't occur when using the "Properties" view (`Right-Click a material > Properties...` towards the bottom of the menu).
* This bug doesn't occur if the first inspector after a domain reload is a material inspector. Any other inspection afterward will have the bug.
* De-selecting and re-selecting the material will show the updated preview mesh (as expected because we are reading it from editor prefs on awake)
* I've verified that the instance ID of the `MaterialEditor` that receives `OnSelectedMeshClick` is not the same as the MaterialEditor rendering the preview in `DoRenderPreview`
* The same bug occurs with the light mode button (next to the preview mesh button). It's safe to assume that the whole toolbar is non-functional.