[ET-VK] Adding extract_scalar_or function to extract scalar value or return a default if value at index is none.

Pull Request resolved: #12357
This diff adds a new function `extract_scalar_or` to the `ComputeGraph` class, which extracts a scalar value from a `ValueRef` index. If the value at the index is `None`, it returns a default value.
ghstack-source-id: 296087802
@exported-using-ghexport

Differential Revision: [D78094858](https://our.internmc.facebook.com/intern/diff/D78094858/)

Author: trivedivivek

backends/vulkan/runtime/graph/ComputeGraph.h

@@ -424,6 +424,12 @@ class ComputeGraph final {
   // Scalar Value Extraction
   //
 
+  bool is_scalar_or_none(const ValueRef idx) const {
+    const Value& value = values_.at(idx);
+    return value.isInt() || value.isDouble() || value.isBool() ||
+        value.isNone();
+  }
+
   template <typename T>
   T extract_scalar(const ValueRef idx) {
     Value& value = values_.at(idx);
@@ -439,6 +445,15 @@ class ComputeGraph final {
     VK_THROW("Cannot extract scalar from Value with type ", value.type());
   }
 
+  template <typename T>
+  T extract_scalar_or(const ValueRef idx, const T default_value) {
+    Value& value = values_.at(idx);
+    if (value.isNone()) {
+      return default_value;
+    }
+    return extract_scalar<T>(idx);
+  }
+
   template <typename T>
   std::optional<T> extract_optional_scalar(const ValueRef idx) {
     if (val_is_none(idx)) {