[libcxx-commits] [libcxx] Optimize input_iterator-pair `insert` for std::vector (PR #113768)

[Peng Liu via libcxx-commits]

winner245 wrote:

Summary of the current updates to this PR:
- PR description: This is rewritten to better explain the improvements introduced by this PR.
- Benchmarks: The benchmark test functions have been slightly revised to yield more reliable results. Additionally, all benchmarks have been re-run with larger input sizes to make the comparisons more reliable and stable. 
- Code reusability: reuse `test_iterators.h` to avoid code duplication (The increased number of lines in the code change is due to the required clang-format operation). 

https://github.com/llvm/llvm-project/pull/113768