Fix amqp091->amqp10 shovel with complex headers (backport #13798)

[mergify]

Some AMQP 0.9.1 headers, in particular x-death headers, cannot be set as application properties. Before this change, trying to shovel dead-lettered messages from an AMQP 0.9.1 source to AMQP 1.0 destination would fail with:

reason: {badarg,
            [{unicode,characters_to_binary,
                 [[{table,
                       [{<<"count">>,long,1},
                        {<<"reason">>,longstr,<<"maxlen">>},
                        {<<"queue">>,longstr,<<"tmp">>},
                        {<<"time">>,timestamp,1745575728},
                        {<<"exchange">>,longstr,<<>>},
                        {<<"routing-keys">>,array,
                         [{longstr,<<"tmp">>}]}]}]],
                 [{file,"unicode.erl"},
                  {line,1219},
                  {error_info,#{module => erl_stdlib_errors}}]},
             {amqp10_client_types,utf8,1,
                 [{file,"amqp10_client_types.erl"},{line,99}]},
             {amqp10_msg,'-set_application_properties/2-fun-0-',3,
                 [{file,"amqp10_msg.erl"},{line,385}]},
             {maps,fold_1,4,[{file,"maps.erl"},{line,860}]},
             {amqp10_msg,set_application_properties,2,
                 [{file,"amqp10_msg.erl"},{line,384}]},
             {maps,fold_1,4,[{file,"maps.erl"},{line,860}]},
             {rabbit_amqp10_shovel,forward,4,
                 [{file,"rabbit_amqp10_shovel.erl"},{line,337}]},
             {rabbit_shovel_worker,handle_info,2,
                 [{file,"rabbit_shovel_worker.erl"},{line,104}]}]}

Fixes #13797

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This is an automatic backport of pull request #13798 done by Mergify.