ggml-virtgpu: improve the reliability of the code (#19846)

* ggml-virtgpu-backend: validate the consistency of the received objects

This patch adds consistency checks in the
ggml-virtgpu-backend (running on the host side) to ensure that the
data received from the guest is consistent (valid pointers, valid
sizes and offsets).

* ggml-virtgpu-backend: add fallback/skips for optional ggml backend methods

```
  1. bck->iface.synchronize(bck)
  2. buft->iface.get_alloc_size(buft, op)
  3. buft->iface.get_max_size(buft)
```

these three methods are optional in the GGML interface. `get_max_size`
was already properly defaulted, but `backend sychronize` and `butf
get_max_size` would have segfaulted the backend if not implemented.

* ggml-virtgpu-backend: fix log format missing argument

* ggml-virtgpu-backend: improve the abort message

* ggml-virtgpu-backend: more safety checks

* ggml-virtgpu-backend: new error code

* ggml-virtgpu-backend: initialize all the error codes

* ggml-virtgpu: add a missing comment generated by the code generator

* ggml-virtgpu: add the '[virtgpu]' prefix to the device/buffer names

* ggml-virtgpu: apir_device_buffer_from_ptr: improve the error message

* ggml-virtgpu: shared: make it match the latest api_remoting.h of Virglrenderer APIR

(still unmerged)

* ggml-virtgpu: update the code generator to have dispatch_command_name in a host/guest shared file

* ggml-virtgpu: REMOTE_CALL: fail if the backend returns an error

* docs/backend/VirtGPU.md: indicate that the RAM+VRAM size is limed to 64 GB with libkrun

* ggml-virtgpu: turn off clang-format header ordering for some of the files

Compilation breaks when ordered alphabetically.

* ggml-virtgpu: clang-format

* ggml-virtgpu/backend/shared/api_remoting: better comments for the APIR return codes

ggml/src/ggml-virtgpu/virtgpu-forward-backend.cpp

@@ -17,8 +17,8 @@ ggml_status apir_backend_graph_compute(virtgpu * gpu, ggml_cgraph * cgraph) {
     size_t               cgraph_size = apir_serialize_ggml_cgraph(cgraph, cgraph_data);
 
     virtgpu_shmem   temp_shmem;  // Local storage for large buffers
-    virtgpu_shmem * shmem = &temp_shmem;
-    bool using_shared_shmem = false;
+    virtgpu_shmem * shmem              = &temp_shmem;
+    bool            using_shared_shmem = false;
 
     if (cgraph_size <= gpu->data_shmem.mmap_size) {
         // Lock mutex before using shared data_shmem buffer
@@ -26,7 +26,7 @@ ggml_status apir_backend_graph_compute(virtgpu * gpu, ggml_cgraph * cgraph) {
             GGML_ABORT(GGML_VIRTGPU "%s: Failed to lock data_shmem mutex", __func__);
         }
         using_shared_shmem = true;
-        shmem = &gpu->data_shmem;
+        shmem              = &gpu->data_shmem;
     } else if (virtgpu_shmem_create(gpu, cgraph_size, shmem)) {
         GGML_ABORT(GGML_VIRTGPU "%s: Couldn't allocate the guest-host shared buffer", __func__);
     }