Update on "[ET-VK][ez] Fix handling of assert ops"

## Changes

* Apply `RemoveAssertsTransform` as part of `vulkan_preprocess`
* Do not call `RemoveAssertsTransform` before lowering the graph
* Register ops related to asserts to the operator registry as ephemeral ops

## Motivation

assert ops are not implemented in Vulkan, so previously `RemoveAssertsTransform()` is called on the graph before the lowering process.

However, it turns out that the assertion ops are required to properly handle dynamic shapes, because they place constraints on the possible range of symbolic integers. If they are not present, then re-tracing the graph during a recompile (which may occur during a graph transform pass) may fail.

Therefore, instead of calling the transform before lowering, call it inside vulkan_preprocess after a point where subsequent passes will not attempt to trace the graph.

Differential Revision: [D75686048](https://our.internmc.facebook.com/intern/diff/D75686048/)

[ghstack-poisoned]

Author: SS-JIA

backends/vulkan/runtime/VulkanBackend.cpp

@@ -569,7 +569,6 @@ class VulkanBackend final : public ::executorch::runtime::BackendInterface {
 
     if (should_propagate_resize) {
       compute_graph->propagate_resize();
-      compute_graph->encode_execute();
     }
     compute_graph->execute();
 

backends/vulkan/runtime/graph/ComputeGraph.cpp

@@ -712,6 +712,7 @@ void ComputeGraph::propagate_resize() {
   for (std::unique_ptr<ExecuteNode>& node : execute_nodes_) {
     node->trigger_resize(this);
   }
+  encode_execute();
 }
 
 } // namespace vkcompute