[TEMPORARY] cherry-pick of acfea34 (PR facebook#14265) - Work around GCC 12 false positive warning for string::insert (facebook#14265)

Summary:
Work around a warning/linter false positive related to the use of string::insert. The code in question is legal C++, but GCC 12's libstdc++ implementation of string::insert internally uses memcpy, which can trigger undefined behavior warnings when the source and destination overlap.

Pull Request resolved: facebook#14265

Reviewed By: pdillinger

Differential Revision: D91594561

Pulled By: mszeszko-meta

fbshipit-source-id: faa1487aba11a6581bf9ac8eb89442b6e4120427

Author: mszeszko-meta

table/unique_id.cc

@@ -199,12 +199,16 @@ Status GetUniqueIdFromTableProperties(const TableProperties &props,
 }
 
 std::string UniqueIdToHumanString(const std::string &id) {
-  // Not so efficient, but that's OK
-  std::string str = Slice(id).ToString(/*hex*/ true);
-  for (size_t i = 16; i < str.size(); i += 17) {
-    str.insert(i, "-");
+  std::string hex = Slice(id).ToString(/*hex*/ true);
+  std::string result;
+  result.reserve(hex.size() + hex.size() / 16);
+  for (size_t i = 0; i < hex.size(); i++) {
+    if (i > 0 && i % 16 == 0) {
+      result.push_back('-');
+    }
+    result.push_back(hex[i]);
   }
-  return str;
+  return result;
 }
 
 std::string InternalUniqueIdToHumanString(UniqueIdPtr in) {