Fix OpenGL shadow textures not honoring texture type when reusing textures

[Rudolph-B]

Resolves #92091

When attempting to reuse old shadow textures in the compatibility renderer, it did not check whether the texture being reused matched the type of texture it was supposed to create (Cubemap texture for omnilights and 2D texture for spotlights). This led to the unexpected behavior described in #92091.

The solution I implemented now verifies that the new light instance is of the same type as the previous one.

I used this MRP for testing.

[Calinou]

Tested locally (rebased on top of master 05d9854) using the MRP from #92091, it works as expected.

[clayjohn]

This makes sense to me, so I think we should merge it. But I don't understand why we don't see the same issue in the other renderers because the logic for them is the same.

[Rudolph-B]

@clayjohn I haven't checked the mobile renderer, but for the Forward+ renderer, it splits omni-lights into its own function called _shadow_atlas_find_omni_shadows() in servers/rendering/renderer_rd/storage_rd/light_storage.cpp. Copying this behavior to the OpenGL renderer to solve the issue seemed a bit excessive and is likely to result in a few more bugs later on.

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 4.3.1.