### 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)

for (int i = 0; i < multimesh->instances; i++) {
			{
				float *dataptr = w + i * old_stride;
				float *newptr = w + i * multimesh->stride_cache;
				float vals[8] = { dataptr[0], dataptr[1], dataptr[2], dataptr[3], dataptr[4], dataptr[5], dataptr[6], dataptr[7] };
				memcpy(newptr, vals, 8 * 4);
			}
			if (multimesh->xform_format == RS::MULTIMESH_TRANSFORM_3D) {
				float *dataptr = w + i * old_stride + 8;
				float *newptr = w + i * multimesh->stride_cache + 8;
				float vals[8] = { dataptr[0], dataptr[1], dataptr[2], dataptr[3] };
				memcpy(newptr, vals, 4 * 4);
			}
			if (multimesh->uses_colors) {
				float *dataptr = w + i * old_stride + (multimesh->xform_format == RS::MULTIMESH_TRANSFORM_2D ? 8 : 12);
				float *newptr = w + i * multimesh->stride_cache + multimesh->color_offset_cache;
				uint16_t val[4] = { Math::make_half_float(dataptr[0]), Math::make_half_float(dataptr[1]), Math::make_half_float(dataptr[2]), Math::make_half_float(dataptr[3]) };
				memcpy(newptr, val, 2 * 4);
			}
			if (multimesh->uses_custom_data) {
				float *dataptr = w + i * old_stride + (multimesh->xform_format == RS::MULTIMESH_TRANSFORM_2D ? 8 : 12) + (multimesh->uses_colors ? 4 : 0);
				float *newptr = w + i * multimesh->stride_cache + multimesh->custom_data_offset_cache;
				uint16_t val[4] = { Math::make_half_float(dataptr[0]), Math::make_half_float(dataptr[1]), Math::make_half_float(dataptr[2]), Math::make_half_float(dataptr[3]) };
				memcpy(newptr, val, 2 * 4);
			}
		}
		multimesh->data_cache.resize(multimesh->instances * (int)multimesh->stride_cache);
		const float *r = multimesh->data_cache.ptr();
		glBindBuffer(GL_ARRAY_BUFFER, multimesh->buffer);
		glBufferData(GL_ARRAY_BUFFER, multimesh->data_cache.size() * sizeof(float), r, GL_STATIC_DRAW);