vulkaninfo: Call enumerate functions with scratch buffer

This change makes calls using GetVectorInit() to start with an already created
buffer of size 64, allowing for the Vulkan implementation to immediately fill
in the buffer, rather than having to call the enumerate function twice. This
change is primarily motivated to reduce the spam VK_LOADER_DEBUG=all produces
when run with vulkaninfo.

Author: charles-lunarg

vulkaninfo/vulkaninfo.h

@@ -232,15 +232,14 @@ static VKAPI_ATTR VkBool32 VKAPI_CALL DbgCallback(VkDebugReportFlagsEXT msgFlags
 // Helper for robustly executing the two-call pattern
 template <typename T, typename F, typename... Ts>
 auto GetVectorInit(const char *func_name, F &&f, T init, Ts &&...ts) -> std::vector<T> {
-    uint32_t count = 0;
+    uint32_t count = 32;  // Preallocate enough so that most calls only happen once
     std::vector<T> results;
     VkResult err;
     uint32_t iteration_count = 0;
-    uint32_t max_iterations = 3;
+    uint32_t max_iterations = 5;
     do {
-        err = f(ts..., &count, nullptr);
-        if (err) THROW_VK_ERR(func_name, err);
-        results.resize(count, init);
+        count *= 2;
+        results.resize(count);
         err = f(ts..., &count, results.data());
         results.resize(count);
         iteration_count++;