### Godot version

v4.2.beta1.official [b1371806a]

### System information

Ubuntu 22.04.3 LTS 22.04 - X11 - GLES3 (Compatibility) - AMD Radeon RX 560 Series (polaris11, LLVM 15.0.7, DRM 3.42, 5.15.0-88-generic) () - AMD Ryzen 3 1200 Quad-Core Processor (4 Threads)

### Issue description

![image](https://github.com/godotengine/godot/assets/1330325/7a986599-5a68-42a4-beb1-5d3b4bf7db6b)
![image](https://github.com/godotengine/godot/assets/1330325/e8b8546b-b47b-4add-9567-7f70709ab03c)

Culling 3D goes bellow 60 fps even with just about 50 simple animated models. With v4.2.dev6.official [57a6813bb] many more models can be spawned without fps drop. However, both versions do show high cpu usage for culling 3D. Without animations there's barely any usage.

### Steps to reproduce

Spawn models with animation with the Compatibility renderer.

### Minimal reproduction project

[CullMRP.zip](https://github.com/godotengine/godot/files/13400514/CullMRP.zip)

if (dirty_mesh_instance_arrays.first() == nullptr) {
		return; 
	}
	glEnable(GL_RASTERIZER_DISCARD);
	glBindFramebuffer(GL_FRAMEBUFFER, 0);
	
	while (dirty_mesh_instance_arrays.first()) {
		MeshInstance *mi = dirty_mesh_instance_arrays.first()->self();
		Skeleton *sk = skeleton_owner.get_or_null(mi->skeleton);
		
		float base_weight = 1.0;
		if (mi->mesh->blend_shape_count && mi->mesh->blend_shape_mode == RS::BLEND_SHAPE_MODE_NORMALIZED) {
			for (uint32_t i = 0; i < mi->mesh->blend_shape_count; i++) {
				base_weight -= mi->blend_weights[i];
			}
		}
		for (uint32_t i = 0; i < mi->surfaces.size(); i++) {
			if (mi->surfaces[i].vertex_buffer == 0) {
				continue;
			}
			bool array_is_2d = mi->surfaces[i].format_cache & RS::ARRAY_FLAG_USE_2D_VERTICES;
			bool can_use_skeleton = sk != nullptr && sk->use_2d == array_is_2d && (mi->surfaces[i].format_cache & RS::ARRAY_FORMAT_BONES);
			bool use_8_weights = mi->surfaces[i].format_cache & RS::ARRAY_FLAG_USE_8_BONE_WEIGHTS;
			
			if (mi->mesh->blend_shape_count) {
				SkeletonShaderGLES3::ShaderVariant variant = SkeletonShaderGLES3::MODE_BASE_PASS;
				uint64_t specialization = 0;
				specialization |= array_is_2d ? SkeletonShaderGLES3::MODE_2D : 0;
				specialization |= SkeletonShaderGLES3::USE_BLEND_SHAPES;
				if (!array_is_2d) {