Replace all "Filter" field with "Filters" for consistency

In file `api/types/client.go`, some of the "*Options{}" structs own a
`Filters` field while some else have the name of `Filter`, this commit
will rename all `Filter` to `Filters` for consistency. Also `Filters`
is consistent with API with format `/xxx?filters=xxx`, that's why
`Filters` is the right name.

Signed-off-by: Zhang Wei <zhangwei555@huawei.com>

client/task_list_test.go

@@ -45,7 +45,7 @@ func TestTaskList(t *testing.T) {
 		},
 		{
 			options: types.TaskListOptions{
-				Filter: filters,
+				Filters: filters,
 			},
 			expectedQueryParams: map[string]string{
 				"filters": `{"label":{"label1":true,"label2":true}}`,