[ET-VK][ez] Misc fixes related to extension support checking

## Context

Follow up from #7576. Apply two "fixes" that were missed in the first diff:

1. Check device capability for Prepacking nodes as well
2. Remove conditional skips during generated operator correctness tests; rely on the device capability check to determine if a skip is needed.

Differential Revision: [D68035430](https://our.internmc.facebook.com/intern/diff/D68035430/)

[ghstack-poisoned]

Author: SS-JIA

backends/vulkan/runtime/api/containers/Tensor.cpp

@@ -478,13 +478,6 @@ vTensor::vTensor(
   if (storage_type != utils::kBuffer) {
     set_logical_limits(storage_.image_extents_);
   }
-
-  if (dtype == vkapi::kHalf) {
-    VK_CHECK_COND(
-        api::context()->adapter_ptr()->supports_16bit_storage_buffers(),
-        "Half dtype is only available if the physical device supports float16 "
-        "storage buffers!");
-  }
 }
 
 // NOLINTNEXTLINE

backends/vulkan/runtime/graph/ops/PrepackNode.cpp

@@ -68,6 +68,8 @@ api::StagingBuffer PrepackNode::create_staging_buffer(ComputeGraph* graph) {
 void PrepackNode::encode(ComputeGraph* graph) {
   api::Context* const context = graph->context();
 
+  context->check_device_capabilities(shader_);
+
   vTensorPtr packed = graph->get_tensor(packed_);
   api::StagingBuffer staging = create_staging_buffer(graph);
 

backends/vulkan/test/op_tests/utils/gen_computegraph.py

@@ -633,30 +633,6 @@ def gen_graph_exec_code(self, check_output=True) -> str:
 
         return graph_exec
 
-    def gen_conditional_skips(self, skip_str: str = "GTEST_SKIP();") -> str:
-        fp16_skip = f"if (!{self.graph}{self.dot}context()->adapter_ptr()->has_full_float16_buffers_support()) {{\n"
-        fp16_skip += f"  {skip_str}\n"
-        fp16_skip += "}"
-        fp16_skip = re.sub(r"^", "  ", fp16_skip, flags=re.M) + "\n"
-
-        int8_skip = f"if (!{self.graph}{self.dot}context()->adapter_ptr()->has_full_int8_buffers_support()) {{\n"
-        int8_skip += f"  {skip_str};\n"
-        int8_skip += "}\n"
-
-        skips = ""
-
-        skips += "if (test_dtype == at::kHalf) {\n"
-        skips += fp16_skip
-        skips += "}\n"
-
-        for _, dtype in self.suite_def.arg_dtype.items():
-            if dtype == "at::kChar" or dtype == "at::kQInt8":
-                skips += int8_skip
-                continue
-
-        skips += "\n"
-        return skips
-
     def gen_op_check_fn(self) -> str:
         op_name = self.f.func.name.unambiguous_name()
         if self.suite_def.test_name_suffix is not None:
@@ -667,7 +643,6 @@ def gen_op_check_fn(self) -> str:
             op_check_fn = self.gen_decl(f"prepacked_check_{op_name}") + " {\n"
 
         op_check_fn_body = ""
-        op_check_fn_body += self.gen_conditional_skips()
         op_check_fn_body += self.gen_graph_build_code()
         op_check_fn_body += self.gen_graph_exec_code()