Use std::copy/std::copy_n in literal-accumulator overload of _AppendRuns

Agent-Logs-Url: https://github.com/Cpp2Rust/cpp2rust/sessions/c9bd1adc-01f6-415e-a50c-9e8a4cb1e414

Co-authored-by: nunoplopes <2998477+nunoplopes@users.noreply.github.com>

Author: Copilot

cpp2rust/converter/converter.h

@@ -7,6 +7,7 @@
 #include <clang/AST/RecursiveASTVisitor.h>
 #include <clang/Sema/Sema.h>
 
+#include <algorithm>
 #include <array>
 #include <functional>
 #include <optional>
@@ -340,10 +341,8 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
   static void _AppendRuns(std::string &rs_code, std::array<char, BufSize> buf,
                           const char (&val)[N], const Rest &...rest) {
     std::array<char, BufSize + N> new_buf;
-    for (std::size_t i = 0; i < BufSize; ++i)
-      new_buf[i] = buf[i];
-    for (std::size_t i = 0; i < N - 1; ++i)
-      new_buf[BufSize + i] = val[i];
+    std::copy(buf.begin(), buf.end(), new_buf.begin());
+    std::copy_n(val, N - 1, new_buf.begin() + BufSize);
     new_buf[BufSize + N - 1] = ' ';
     _AppendRuns(rs_code, new_buf, rest...);
   }