The UVM field macros enclosed within the _utils_begin/end block define sections of a function that is invoked by apply_config_settings(), which in turn calls uvm_config_db#(type)::get(), which is subsequently called by uvm_component::build_phase(). See Comprehension question: apply_config_settings, config_db,.
uvm_config_db#(uvm_bitstream_t) and uvm_config_db#(int) map to different databases. See Difference between set_config_object and uvm_config_db #(...)::set(); - #2 by dave_59