clang-tidy: performance-inefficient-vector-operation (#7471)

Signed-off-by: Derek Argueta <dereka@pinterest.com>

.clang-tidy

@@ -24,6 +24,7 @@ WarningsAsErrors: 'abseil-duration-*,
                    modernize-use-using,
                    performance-faster-string-find,
                    performance-for-range-copy,
+                   performance-inefficient-vector-operation,
                    performance-noexcept-move-constructor,
                    performance-unnecessary-copy-initialization,
                    readability-braces-around-statements,

source/server/http/admin.cc

@@ -825,6 +825,7 @@ std::string PrometheusStatsFormatter::sanitizeName(const std::string& name) {
 
 std::string PrometheusStatsFormatter::formattedTags(const std::vector<Stats::Tag>& tags) {
   std::vector<std::string> buf;
+  buf.reserve(tags.size());
   for (const Stats::Tag& tag : tags) {
     buf.push_back(fmt::format("{}=\"{}\"", sanitizeName(tag.name_), tag.value_));
   }

test/integration/integration.cc

@@ -341,6 +341,7 @@ void BaseIntegrationTest::createEnvoy() {
 
   std::vector<std::string> named_ports;
   const auto& static_resources = config_helper_.bootstrap().static_resources();
+  named_ports.reserve(static_resources.listeners_size());
   for (int i = 0; i < static_resources.listeners_size(); ++i) {
     named_ports.push_back(static_resources.listeners(i).name());
   }

test/server/options_impl_test.cc

@@ -1,3 +1,4 @@
+#include <algorithm>
 #include <chrono>
 #include <fstream>
 #include <memory>
@@ -37,9 +38,8 @@ class OptionsImplTest : public testing::Test {
   std::unique_ptr<OptionsImpl> createOptionsImpl(const std::string& args) {
     std::vector<std::string> words = TestUtility::split(args, ' ');
     std::vector<const char*> argv;
-    for (const std::string& s : words) {
-      argv.push_back(s.c_str());
-    }
+    std::transform(words.cbegin(), words.cend(), std::back_inserter(argv),
+                   [](const std::string& arg) { return arg.c_str(); });
     return std::make_unique<OptionsImpl>(
         argv.size(), argv.data(), [](bool) { return "1"; }, spdlog::level::warn);
   }