Fix ZDB to dump projid for projectquota enabled (openzfs#16291)

ZDB is supposed to dump "projid" via dump_znode(), when projectquota
is enabled.
-----------
static void
dump_znode(objset_t *os, uint64_t object, void *data, size_t size)
{
...
    if (dmu_objset_projectquota_enabled(os) && (pflags & ZFS_PROJID)) {
	uint64_t projid;

	if (sa_lookup(hdl, sa_attr_table[ZPL_PROJID], &projid,
	    sizeof (uint64_t)) == 0)
		(void) printf("\tprojid %llu\n", (u_longlong_t)projid);
    }
...
}
----------
But its not dumping "projid", even for project quota enabled.

dmu_objset_projectquota_enabled() does following 3 checks,
----------
boolean_t
dmu_objset_projectquota_enabled(objset_t *os)
{
        return (file_cbs[os->os_phys->os_type] != NULL &&
            DMU_PROJECTUSED_DNODE(os) != NULL &&
            spa_feature_is_enabled(os->os_spa,
		SPA_FEATURE_PROJECT_QUOTA));
}
----------
It fails on file_cbs[] check. file_cbs[] gets initialised via
dmu_objset_register_type(); which is not done for the ZDB, its done for
the kernel via zfs_init().

Register a dummy callback handle for the DMU_OST_ZFS type in
ZDB main() function to dump the projid for projectquota enabled.

Signed-off-by: Jitendra Patidar <[email protected]>
Closes openzfs#16290
Reviewed-by: Tony Hutter <[email protected]>
Reviewed-by: Tino Reichardt <[email protected]>

cmd/zdb/zdb.c

@@ -8932,6 +8932,19 @@ zdb_numeric(char *str)
 	return (B_TRUE);
 }
 
+static int
+dummy_get_file_info(dmu_object_type_t bonustype, const void *data,
+    zfs_file_info_t *zoi)
+{
+	(void) data, (void) zoi;
+
+	if (bonustype != DMU_OT_ZNODE && bonustype != DMU_OT_SA)
+		return (ENOENT);
+
+	(void) fprintf(stderr, "dummy_get_file_info: not implemented");
+	abort();
+}
+
 int
 main(int argc, char **argv)
 {
@@ -9247,6 +9260,7 @@ main(int argc, char **argv)
 		libzfs_core_fini();
 	}
 
+	dmu_objset_register_type(DMU_OST_ZFS, dummy_get_file_info);
 	kernel_init(SPA_MODE_READ);
 	kernel_init_done = B_TRUE;