Mostly remove pre-CXX11 workarounds.

С++03 support was deprecated in 1.85 and now can be removed. This PR clears
many of workarounds, which are no longer needed now.

* Remove unused workaround macros (many of).
* Remove BOOST_STATIC_ASSERT usages.
* Minimize Boost::type_traits dependency (in favour of STL's type_traits).

Closes https://github.com/boostorg/iterator/pull/82.

Squashed commit of the following:

commit 741a627b73
Author: Georgy Guminov <gogagum@gmail.com>
Date:   Sat Jan 25 12:13:05 2025 +0300

    Replace testers with standard metafunctions.

commit bf4cce6114
Author: Georgy Guminov <gogagum@gmail.com>
Date:   Sat Jan 25 11:51:32 2025 +0300

    Refactor is_lvalue_iterator.hpp.

commit 8d080c6c58
Author: Georgy Guminov <gogagum@gmail.com>
Date:   Sat Jan 25 10:27:32 2025 +0300

    Remove more workarounds.

commit 5a4ba24d36
Author: Georgy Guminov <gogagum@gmail.com>
Date:   Sun Jan 19 16:38:30 2025 +0300

    Fixes.

commit fdfafce2b9
Author: Georgy Guminov <gogagum@gmail.com>
Date:   Sat Oct 26 15:06:43 2024 +0300

    Remove BOOST_NO_STRICT_ITERATOR_INTEROPERABILITY
    Correct static_assert messages.
    Fix messages & replace is_standard_layout with is_copy_constructible.

commit c69ac1408a
Author: Georgy Guminov <gogagum@gmail.com>
Date:   Sat Oct 26 14:48:51 2024 +0300

    Correct static_assert messages.

commit b5df827151
Author: Georqy Guminov <gogagum@gmail.com>
Date:   Sun Jun 23 16:12:29 2024 +0300

    Fixes. Remove some Boost.MPL usages. Remove unused includes.

commit 01fd35e9f8
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Wed Jun 12 17:14:21 2024 +0300

    abstract conjunction.

commit c02def8acf
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Wed Jun 12 16:35:43 2024 +0300

    return addressof & conjunction.

commit 3b3d162575
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Wed Jun 12 16:30:44 2024 +0300

    Make macro more readable.

commit 4ab19e045f
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Wed Jun 12 15:56:49 2024 +0300

    Add static_assert messages.

commit 82b5c44cd3
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Wed Jun 12 14:12:10 2024 +0300

    Return is iterator CXX17 test.

commit 2d58d65462
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Tue Jun 11 14:04:17 2024 +0300

    Omitted.

commit a0d04d9491
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Tue Jun 11 14:00:35 2024 +0300

    Replace move with static_cast

commit 4a49b8a1a2
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Mon Jun 10 21:38:53 2024 +0300

    Return BOOST_NOEXCEPT

commit 054c013bba
Author: Georgiy Guminov <gogagum@gmail.com>
Date:   Sun Jun 9 15:20:41 2024 +0300

    CXX11

test/iterator_adaptor_test.cpp

@@ -13,10 +13,8 @@
 #include <numeric>
 
 #include <boost/iterator/iterator_adaptor.hpp>
-#if !BOOST_WORKAROUND(__MWERKS__, <= 0x2407)
-# include <boost/iterator/is_readable_iterator.hpp>
-# include <boost/iterator/is_lvalue_iterator.hpp>
-#endif
+#include <boost/iterator/is_readable_iterator.hpp>
+#include <boost/iterator/is_lvalue_iterator.hpp>
 #include <boost/pending/iterator_tests.hpp>
 
 # include <boost/core/lightweight_test.hpp>
@@ -29,8 +27,6 @@
 
 #include "static_assert_same.hpp"
 
-#include <boost/iterator/detail/config_def.hpp>
-
 using boost::dummyT;
 
 typedef std::deque<int> storage;
@@ -56,9 +52,6 @@ struct ptr_iterator
       , V*
       , V
       , boost::random_access_traversal_tag
-#if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x551))
-      , V&
-#endif
    >
 {
 private:
@@ -67,9 +60,6 @@ private:
       , V*
       , V
       , boost::random_access_traversal_tag
-#if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x551))
-      , V&
-#endif
     > super_t;
 
 public:
@@ -208,9 +198,10 @@ main()
     test = static_assert_same<Iter1::reference, int&>::value;
     test = static_assert_same<Iter1::pointer, int*>::value;
     test = static_assert_same<Iter1::difference_type, std::ptrdiff_t>::value;
-#if !BOOST_WORKAROUND(__MWERKS__, <= 0x2407)
-    BOOST_STATIC_ASSERT((boost::is_convertible<Iter1::iterator_category, std::random_access_iterator_tag>::value));
-#endif
+    static_assert(
+        std::is_convertible<Iter1::iterator_category, std::random_access_iterator_tag>::value,
+        "Iterator must have a random access category."
+    );
   }
 
   {
@@ -219,16 +210,10 @@ main()
     test = static_assert_same<Iter1::value_type, int>::value;
     test = static_assert_same<Iter1::reference, const int&>::value;
 
-#if !BOOST_WORKAROUND(__MWERKS__, <= 0x2407)
-    BOOST_STATIC_ASSERT(boost::is_readable_iterator<Iter1>::value);
-# ifndef BOOST_NO_LVALUE_RETURN_DETECTION
-    BOOST_STATIC_ASSERT(boost::is_lvalue_iterator<Iter1>::value);
-# endif
-#endif
+    static_assert(boost::is_readable_iterator<Iter1>::value, "Iter1 is expected to be readable.");
+    static_assert(boost::is_lvalue_iterator<Iter1>::value, "Iter1 is expected to be lvalue iterator.");
 
-#if !BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564)) // borland drops constness
     test = static_assert_same<Iter1::pointer, int const*>::value;
-#endif
   }
 
   {
@@ -238,14 +223,16 @@ main()
 
     test = static_assert_same<Iter::value_type, int>::value;
     test = static_assert_same<Iter::reference, int const&>::value;
-#if !BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564)) // borland drops constness
     test = static_assert_same<Iter::pointer, int const*>::value;
-#endif
 
-#ifndef BOOST_NO_LVALUE_RETURN_DETECTION
-    BOOST_STATIC_ASSERT(boost::is_non_const_lvalue_iterator<BaseIter>::value);
-    BOOST_STATIC_ASSERT(boost::is_lvalue_iterator<Iter>::value);
-#endif
+    static_assert(
+      boost::is_non_const_lvalue_iterator<BaseIter>::value,
+      "boost::is_non_const_lvalue_iterator<BaseIter>::value is expected to be true."
+    );
+    static_assert(
+      boost::is_lvalue_iterator<Iter>::value,
+      "boost::is_lvalue_iterator<Iter>::value is expected to be true."
+    );
 
     typedef modify_traversal<BaseIter, boost::incrementable_traversal_tag> IncrementableIter;