Fix instance uniform data buffer update delay

[bitsawer]

• Fixes Shader instance uniforms are updated with one frame delay #79602

This PR simply moves dirty resource updates after instance updates, as instance updates can cause some resources to become dirty. This can cause an extra frame of delay when updating instance uniforms, multimesh data or particle data. For example in the MRP project in the linked issue, the update order currently goes like this:

1. User code calls set_instance_shader_parameter(), data is sent to server.
2. Rendering loop eventually calls RendererSceneCull::update_dirty_instances().
3. RSG::utilities->update_dirty_resources() updates dirty resources, more importantly in this scenario it calls MaterialStorage::get_singleton()->_update_global_shader_uniforms() which buffer_update()'s dirty instance+global uniform data to GPU.
4. Rendering code loops through dirty instances, calls _update_dirty_instance() for each of them and marks resources as dirty, including instance uniform buffer.

This PR basically reverses the order of steps 3 and 4. Because step 4 can actually mark resources as dirty but as the dirty resources were already uploaded to GPU in step 3 this will cause one frame update delay.

I tested this PR with some more complex demos and didn't notice any regressions, but these issues can be pretty subtle to notice.

Also, if this PR is accepted, the same reordering should probably done to this PR #77594 as it adds RendererCanvasCull::update_dirty_instances() which is functionally similar to RendererSceneCull implementation.

[clayjohn]

I looked carefully through _update_dirty_instance() and I can't see anything that would require the resources to be updated first (i.e. it isn't reading back any data that should be changed).

Therefore, I think this is safe to merge.

Because of the complexity of _update_dirty_instance(), I consider this a higher than normal risk merge, so we should not cherrypick this to a previous version.

[YuriSizov]

Thanks!