build: disable boost multi index safe mode

Disable boost multi index safe mode by default when configuring with
--enable-debug.

This option can cause transactions to take a long time to be accepted
into the mempool under certain conditions; iterator destruction takes
O(n) time vs O(1) as they are stored in a singly linked list. See
27586 for more information.

Re-enable it on the CI builds which previously had it enabled.

Re-enable it on the msan fuzz target so that we have fuzz tasks testing
with it enabeld and disabled in this repo.

Github-Pull: #27724
Rebased-From: 59c8944749

configure.ac

@@ -1482,10 +1482,6 @@ if test "$use_boost" = "yes"; then
   AX_CHECK_PREPROC_FLAG([-DBOOST_NO_CXX98_FUNCTION_BASE], [BOOST_CPPFLAGS="$BOOST_CPPFLAGS -DBOOST_NO_CXX98_FUNCTION_BASE"], [], [$CXXFLAG_WERROR],
                         [AC_LANG_PROGRAM([[#include <boost/config.hpp>]])])
 
-  if test "$enable_debug" = "yes" || test "$enable_fuzz" = "yes"; then
-    BOOST_CPPFLAGS="$BOOST_CPPFLAGS -DBOOST_MULTI_INDEX_ENABLE_SAFE_MODE"
-  fi
-
   if test "$suppress_external_warnings" != "no"; then
     BOOST_CPPFLAGS=SUPPRESS_WARNINGS($BOOST_CPPFLAGS)
   fi