[libc++][vector] Inline remaining constructors filling vector with the same value (#82068)

Placing physically next to each other remaining constructors filling
vector with the same value
will make code better, since they all have nearly identical
implementation, which needs to be kept in sync.

Co-authored-by: Mark de Wever <[email protected]>

Author: mtezych

libcxx/include/vector

@@ -424,11 +424,36 @@ public:
 #endif
       : __end_cap_(nullptr, __a) {
   }
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI explicit vector(size_type __n);
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI explicit vector(size_type __n) {
+    auto __guard = std::__make_exception_guard(__destroy_vector(*this));
+    if (__n > 0) {
+      __vallocate(__n);
+      __construct_at_end(__n);
+    }
+    __guard.__complete();
+  }
+
 #if _LIBCPP_STD_VER >= 14
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI explicit vector(size_type __n, const allocator_type& __a);
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI explicit vector(size_type __n, const allocator_type& __a)
+      : __end_cap_(nullptr, __a) {
+    auto __guard = std::__make_exception_guard(__destroy_vector(*this));
+    if (__n > 0) {
+      __vallocate(__n);
+      __construct_at_end(__n);
+    }
+    __guard.__complete();
+  }
 #endif
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI vector(size_type __n, const value_type& __x);
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI vector(size_type __n, const value_type& __x) {
+    auto __guard = std::__make_exception_guard(__destroy_vector(*this));
+    if (__n > 0) {
+      __vallocate(__n);
+      __construct_at_end(__n, __x);
+    }
+    __guard.__complete();
+  }
 
   template <__enable_if_t<__is_allocator<_Allocator>::value, int> = 0>
   _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI
@@ -1125,39 +1150,6 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void vector<_Tp, _Allocator>::__append(size_type _
   }
 }
 
-template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20 vector<_Tp, _Allocator>::vector(size_type __n) {
-  auto __guard = std::__make_exception_guard(__destroy_vector(*this));
-  if (__n > 0) {
-    __vallocate(__n);
-    __construct_at_end(__n);
-  }
-  __guard.__complete();
-}
-
-#if _LIBCPP_STD_VER >= 14
-template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20 vector<_Tp, _Allocator>::vector(size_type __n, const allocator_type& __a)
-    : __end_cap_(nullptr, __a) {
-  auto __guard = std::__make_exception_guard(__destroy_vector(*this));
-  if (__n > 0) {
-    __vallocate(__n);
-    __construct_at_end(__n);
-  }
-  __guard.__complete();
-}
-#endif
-
-template <class _Tp, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20 vector<_Tp, _Allocator>::vector(size_type __n, const value_type& __x) {
-  auto __guard = std::__make_exception_guard(__destroy_vector(*this));
-  if (__n > 0) {
-    __vallocate(__n);
-    __construct_at_end(__n, __x);
-  }
-  __guard.__complete();
-}
-
 template <class _Tp, class _Allocator>
 template <class _InputIterator,
           __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value &&