worker_spi: Use term "dynamic" for bgworkers launched with worker_spi_launch()

This gives a way to make a difference between workers registered when
the library is loaded with shared_preload_libraries and when these are
launched dynamically, in ps output or pg_stat_activity.

Extracted from a larger patch by the same author.

Author: Bharath Rupireddy
Reviewed-by: Masahiro Ikeda
Discussion: https://postgr.es/m/CALj2ACWR9ncAiDF73unqdJF1dmsA2R0efGXX2624X+YVxcAVWg@mail.gmail.com

src/test/modules/worker_spi/worker_spi.c

@@ -370,8 +370,8 @@ worker_spi_launch(PG_FUNCTION_ARGS)
 	worker.bgw_restart_time = BGW_NEVER_RESTART;
 	sprintf(worker.bgw_library_name, "worker_spi");
 	sprintf(worker.bgw_function_name, "worker_spi_main");
-	snprintf(worker.bgw_name, BGW_MAXLEN, "worker_spi worker %d", i);
-	snprintf(worker.bgw_type, BGW_MAXLEN, "worker_spi");
+	snprintf(worker.bgw_name, BGW_MAXLEN, "worker_spi dynamic worker %d", i);
+	snprintf(worker.bgw_type, BGW_MAXLEN, "worker_spi dynamic");
 	worker.bgw_main_arg = Int32GetDatum(i);
 	/* set bgw_notify_pid so that we can use WaitForBackgroundWorkerStartup */
 	worker.bgw_notify_pid = MyProcPid;