ADIOS 2.10.1: `int64_t` in `CampaignData.h` missing include & namespace

[ax3l]

Compile issue:

  [ 72%] Building CXX object source/adios2/CMakeFiles/adios2_core.dir/engine/campaign/CampaignReader.cpp.o
  cd /project/build-adios2/source/adios2 && /usr/bin/c++  -I/project/ADIOS2-2.10.1/source -I/project/build-adios2/source -I/project/build-adios2/thirdparty/KWSys/adios2sys -I/project/ADIOS2-2.10.1/thirdparty/pugixml/pugixml/src -I/project/ADIOS2-2.10.1/thirdparty/yaml-cpp/yaml-cpp/include -I/project/ADIOS2-2.10.1/thirdparty/nlohmann_json/nlohmann_json_wrapper -I/project/ADIOS2-2.10.1/thirdparty/nlohmann_json/nlohmann_json_wrapper/single_include -I/project/build-adios2/thirdparty/perfstubs -I/project/ADIOS2-2.10.1/thirdparty/ffs/ffs -I/project/ADIOS2-2.10.1/thirdparty/ffs/ffs/fm -I/project/ADIOS2-2.10.1/thirdparty/ffs/ffs/cod -I/project/ADIOS2-2.10.1/thirdparty/ffs/ffs/ffs -I/project/build-adios2/thirdparty/ffs/ffs -I/project/build-adios2/thirdparty/ffs/ffs/ffs -I/project/ADIOS2-2.10.1/thirdparty/atl/atl -I/project/build-adios2/thirdparty/atl/atl -I/project/build-adios2/thirdparty/EVPath/EVPath -I/project/ADIOS2-2.10.1/thirdparty/EVPath/EVPath -fPIC -O3 -DNDEBUG -std=c++11 -fPIC -MD -MT source/adios2/CMakeFiles/adios2_core.dir/engine/campaign/CampaignReader.cpp.o -MF CMakeFiles/adios2_core.dir/engine/campaign/CampaignReader.cpp.o.d -o CMakeFiles/adios2_core.dir/engine/campaign/CampaignReader.cpp.o -c /project/ADIOS2-2.10.1/source/adios2/engine/campaign/CampaignReader.cpp
  In file included from /project/ADIOS2-2.10.1/source/adios2/engine/campaign/CampaignReader.h:15,
                   from /project/ADIOS2-2.10.1/source/adios2/engine/campaign/CampaignReader.cpp:11:
  /project/ADIOS2-2.10.1/source/adios2/engine/campaign/CampaignData.h:44:5: error: 'int64_t' does not name a type
     44 |     int64_t ctime;
        |     ^~~~~~~
  /project/ADIOS2-2.10.1/source/adios2/engine/campaign/CampaignData.h:22:1: note: 'int64_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
     21 | #include <sqlite3.h>
    +++ |+#include <cstdint>
     22 | 

System:
GCC 13.2.1 on musllinux

X-ref: openPMD/openPMD-api#1554