[EK-VT] Adding reserve and append functions to SpecVarList

This diff adds two new functions to the SpecVarList class in the Vulkan runtime library. The first function, reserve, allows the user to reserve a certain amount of space in the SpecVarList before adding any elements. The second function, append, allows the user to add a single SpecVar to the SpecVarList. These functions are useful for optimizing memory usage and improving performance in the Vulkan runtime.

Differential Revision: [D70021782](https://our.internmc.facebook.com/intern/diff/D70021782/)

ghstack-source-id: 267791088
Pull Request resolved: #8633

Author: trivedivivek

backends/vulkan/runtime/vk_api/Pipeline.cpp

@@ -174,6 +174,14 @@ void SpecVarList::append(const SpecVarList& other) {
   vars.insert(vars.end(), other.vars.begin(), other.vars.end());
 }
 
+void SpecVarList::reserve(const size_t size) {
+  vars.reserve(size);
+}
+
+void SpecVarList::append(const SpecVar& other) {
+  vars.push_back(other);
+}
+
 std::vector<VkSpecializationMapEntry> SpecVarList::generate_map_entries()
     const {
   std::vector<VkSpecializationMapEntry> map_entries;

backends/vulkan/runtime/vk_api/Pipeline.h

@@ -82,6 +82,10 @@ class SpecVarList final {
 
   void append(const SpecVarList& other);
 
+  void reserve(const size_t size);
+
+  void append(const SpecVar& other);
+
   std::vector<VkSpecializationMapEntry> generate_map_entries() const;
 
   friend bool operator==(const SpecVarList& lhs, const SpecVarList& rhs);