Add rdcarray helper for "resize array up to this index if smaller"

* This is a common enough operation to warrant a helper, as an alternative to
  vec.resize(RDCMAX(index + 1, vec.size())

renderdoc/api/replay/rdcarray.h

@@ -251,6 +251,16 @@ public:
     allocatedCount = s;
   }
 
+  void resize_for_index(size_t s)
+  {
+    // do nothing if we're already big enough
+    if(size() >= s + 1)
+      return;
+
+    // otherwise resize so that [s] is valid
+    resize(s + 1);
+  }
+
   void resize(size_t s)
   {
     // do nothing if we're already this size

renderdoc/replay/basic_types_tests.cpp

@@ -463,6 +463,43 @@ TEST_CASE("Test array type", "[basictypes]")
     CHECK(vec[1] == 5);
   };
 
+  SECTION("resize_for_index")
+  {
+    rdcarray<int> test;
+
+    CHECK(test.empty());
+
+    test.resize_for_index(0);
+
+    CHECK(test.size() == 1);
+    CHECK(test.capacity() >= 1);
+
+    test.resize_for_index(5);
+
+    CHECK(test.size() == 5);
+    CHECK(test.capacity() >= 5);
+
+    test.resize_for_index(5);
+
+    CHECK(test.size() == 5);
+    CHECK(test.capacity() >= 5);
+
+    test.resize_for_index(3);
+
+    CHECK(test.size() == 5);
+    CHECK(test.capacity() >= 5);
+
+    test.resize_for_index(0);
+
+    CHECK(test.size() == 5);
+    CHECK(test.capacity() >= 5);
+
+    test.resize_for_index(9);
+
+    CHECK(test.size() == 9);
+    CHECK(test.capacity() >= 9);
+  };
+
   SECTION("Check construction")
   {
     rdcarray<ConstructorCounter> test;