Fix buffer size issue in filter name generation

[ShangzhiXu]

The compiler complain frequently when I compile with EXTENDED_FILTERING

 cmake .. \
  -DCMAKE_BUILD_TYPE=Debug \
  -DWITH_DLT_DEBUGGERS=ON \
  -DWITH_EXTENDED_FILTERING=ON

The warnings are

/home/shangzhi/fuz/fix/dlt-daemon/src/console/dlt-control-common.c: In function ‘dlt_json_filter_save’:
/home/shangzhi/fuz/fix/dlt-daemon/src/console/dlt-control-common.c:922:25: error: cast discards ‘const’ qualifier from pointer target type [-Werror=cast-qual]
  922 |     json_object_to_file((char*)filename, json_filter_obj);
      |                         ^
/home/shangzhi/fuz/fix/dlt-daemon/src/console/dlt-control-common.c:901:39: error: ‘sprintf’ may write a terminating nul past the end of the destination [-Werror=format-overflow=]
  901 |         sprintf(filter_name, "filter%i", num);
      |                                       ^
/home/shangzhi/fuz/fix/dlt-daemon/src/console/dlt-control-common.c:901:9: note: ‘sprintf’ output between 8 and 17 bytes into a destination of size 16
  901 |         sprintf(filter_name, "filter%i", num);

I fixed with snprintf and removed the casting