[libc++] Fix vector sanitization annotations on destruction

In D144155/D136765, the asan annotations for `std::vector` were modified to unpoison freed backing memory on destruction, instead of leaving it
poisoned. However, calling `__clear()` instead of `clear()` skips informing the asan runtime of this decrease in the accessible container size, which
breaks the invariant that the value of `old_mid` should match the value of `new_mid` from the previous call to `__sanitizer_annotate_contiguous_container`,
which can trip the sanity checks for the partial poison between [d1, d2) and the container redzone between [d2, c), if enabled. To fix this, ensure that
`clear()` is called instead, as is already done by `__vdeallocate()`. Also remove `__clear()`, since it is no longer called.

Author: ddcc

libcxx/include/__vector/vector.h

@@ -241,7 +241,7 @@ class _LIBCPP_TEMPLATE_VIS vector {
 
     _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void operator()() {
       if (__vec_.__begin_ != nullptr) {
-        __vec_.__clear();
+        __vec_.clear();
         __vec_.__annotate_delete();
         __alloc_traits::deallocate(__vec_.__alloc_, __vec_.__begin_, __vec_.capacity());
       }
@@ -520,7 +520,7 @@ class _LIBCPP_TEMPLATE_VIS vector {
 
   _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void clear() _NOEXCEPT {
     size_type __old_size = size();
-    __clear();
+    __base_destruct_at_end(this->__begin_);
     __annotate_shrink(__old_size);
   }
 
@@ -732,10 +732,6 @@ class _LIBCPP_TEMPLATE_VIS vector {
     ++__tx.__pos_;
   }
 
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __clear() _NOEXCEPT {
-    __base_destruct_at_end(this->__begin_);
-  }
-
   _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __base_destruct_at_end(pointer __new_last) _NOEXCEPT {
     pointer __soon_to_be_end = this->__end_;
     while (__new_last != __soon_to_be_end)
@@ -759,7 +755,7 @@ class _LIBCPP_TEMPLATE_VIS vector {
 
   _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const vector& __c, true_type) {
     if (this->__alloc_ != __c.__alloc_) {
-      __clear();
+      clear();
       __annotate_delete();
       __alloc_traits::deallocate(this->__alloc_, this->__begin_, capacity());
       this->__begin_ = this->__end_ = this->__cap_ = nullptr;