[container.reqmts] Move requirements to the right place (cplusplus#6199)

As part of the replacement of the container requirements tables with text,
several paragraphs of general container requirements were buried
in the new subsections for more specific requirements such as
reversible containers or allocator-aware containers.

This seems to have happened when general container requirements
followed one of the container requirements tables that are now expressed
as text. This change carefully restores text to the general container requirements
clause, in the original order they appeared in C++20.

Author: AlisdairM

source/containers.tex

@@ -636,6 +636,57 @@
 with value \tcode{a.end()} before the swap will have value \tcode{b.end()} after the
 swap.
 
+\pnum
+Unless otherwise specified (see~\ref{associative.reqmts.except}, \ref{unord.req.except}, \ref{deque.modifiers}, and
+\ref{vector.modifiers})
+all container types defined in this Clause meet
+the following additional requirements:
+
+\begin{itemize}
+\item
+If an exception is thrown by an
+\tcode{insert()} or \tcode{emplace()}
+function while inserting a single element, that
+function has no effects.
+\item
+If an exception is thrown by a
+\tcode{push_back()},
+\tcode{push_front()},
+\tcode{emplace_back()}, or \tcode{emplace_front()}
+function, that function has no effects.
+\item
+No
+\tcode{erase()},
+\tcode{clear()},
+\tcode{pop_back()}
+or
+\tcode{pop_front()}
+function throws an exception.
+\item
+No copy constructor or assignment operator of a returned iterator
+throws an exception.
+\item
+No
+\tcode{swap()}
+function throws an exception.
+\item
+No
+\tcode{swap()}
+function invalidates any references,
+pointers, or iterators referring to the elements
+of the containers being swapped.
+\begin{note}
+The \tcode{end()} iterator does not refer to any element, so it can be invalidated.
+\end{note}
+\end{itemize}
+
+\pnum
+Unless otherwise specified (either explicitly or by defining a
+function in terms of other functions), invoking a container member
+function or passing a container as an argument to a library function
+shall not invalidate iterators to, or change the values of, objects
+within that container.
+
 \pnum
 A \defnadj{contiguous}{container}
 is a container
@@ -644,6 +695,24 @@
 \oldconcept{RandomAccessIterator} requirements\iref{random.access.iterators} and
 model \libconcept{contiguous_iterator}\iref{iterator.concept.contiguous}.
 
+\pnum
+The behavior of certain container member functions and deduction guides
+depends on whether types qualify as input iterators or allocators.
+The extent to which an implementation determines that a type cannot be an input
+iterator is unspecified, except that as a minimum integral types shall not qualify
+as input iterators.
+Likewise, the extent to which an implementation determines that a type cannot be
+an allocator is unspecified, except that as a minimum a type \tcode{A} shall not qualify
+as an allocator unless it meets both of the following conditions:
+
+\begin{itemize}
+\item The \grammarterm{qualified-id} \tcode{A::value_type}
+is valid and denotes a type\iref{temp.deduct}.
+
+\item The expression \tcode{declval<A\&>().allocate(size_t\{\})}
+is well-formed when treated as an unevaluated operand.
+\end{itemize}
+
 \rSec3[container.rev.reqmts]{Reversible container requirements}
 
 % Local command to index names as members of all containers.
@@ -774,56 +843,6 @@
 Constant.
 \end{itemdescr}
 
-\pnum
-Unless otherwise specified (see~\ref{associative.reqmts.except}, \ref{unord.req.except}, \ref{deque.modifiers}, and
-\ref{vector.modifiers})
-all container types defined in this Clause meet
-the following additional requirements:
-
-\begin{itemize}
-\item
-If an exception is thrown by an
-\tcode{insert()} or \tcode{emplace()}
-function while inserting a single element, that
-function has no effects.
-\item
-If an exception is thrown by a
-\tcode{push_back()},
-\tcode{push_front()},
-\tcode{emplace_back()}, or \tcode{emplace_front()}
-function, that function has no effects.
-\item
-No
-\tcode{erase()},
-\tcode{clear()},
-\tcode{pop_back()}
-or
-\tcode{pop_front()}
-function throws an exception.
-\item
-No copy constructor or assignment operator of a returned iterator
-throws an exception.
-\item
-No
-\tcode{swap()}
-function throws an exception.
-\item
-No
-\tcode{swap()}
-function invalidates any references,
-pointers, or iterators referring to the elements
-of the containers being swapped.
-\begin{note}
-The \tcode{end()} iterator does not refer to any element, so it can be invalidated.
-\end{note}
-\end{itemize}
-
-\pnum
-Unless otherwise specified (either explicitly or by defining a
-function in terms of other functions), invoking a container member
-function or passing a container as an argument to a library function
-shall not invalidate iterators to, or change the values of, objects
-within that container.
 
 \rSec3[container.opt.reqmts]{Optional container requirements}
 
@@ -1192,23 +1211,6 @@
 Constant.
 \end{itemdescr}
 
-\pnum
-The behavior of certain container member functions and deduction guides
-depends on whether types qualify as input iterators or allocators.
-The extent to which an implementation determines that a type cannot be an input
-iterator is unspecified, except that as a minimum integral types shall not qualify
-as input iterators.
-Likewise, the extent to which an implementation determines that a type cannot be
-an allocator is unspecified, except that as a minimum a type \tcode{A} shall not qualify
-as an allocator unless it meets both of the following conditions:
-
-\begin{itemize}
-\item The \grammarterm{qualified-id} \tcode{A::value_type}
-is valid and denotes a type\iref{temp.deduct}.
-
-\item The expression \tcode{declval<A\&>().allocate(size_t\{\})}
-is well-formed when treated as an unevaluated operand.
-\end{itemize}
 
 \rSec2[container.requirements.dataraces]{Container data races}