tests/int/checkpoint: add requires criu_feature_xxx

1. A few tests use "criu check --feature" to check for a specific
   feature. Let's generalize it.

2. Fix "checkpoint --pre-dump and restore" test to require memory
   tracking (which is missing on ARM).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

tests/integration/checkpoint.bats

@@ -173,6 +173,10 @@ function simple_cr() {
 }
 
 @test "checkpoint --pre-dump and restore" {
+	# Requires kernel dirty memory tracking (missing on ARM, see
+	# https://github.com/checkpoint-restore/criu/issues/1729).
+	requires criu_feature_mem_dirty_track
+
 	setup_pipes
 	runc_run_with_pipes test_busybox
 
@@ -202,10 +206,8 @@ function simple_cr() {
 }
 
 @test "checkpoint --lazy-pages and restore" {
-	# check if lazy-pages is supported
-	if ! criu check --feature uffd-noncoop; then
-		skip "this criu does not support lazy migration"
-	fi
+	# Requires lazy-pages support.
+	requires criu_feature_uffd-noncoop
 
 	setup_pipes
 	runc_run_with_pipes test_busybox
@@ -274,11 +276,8 @@ function simple_cr() {
 }
 
 @test "checkpoint and restore in external network namespace" {
-	# check if external_net_ns is supported; only with criu 3.10++
-	if ! criu check --feature external_net_ns; then
-		# this criu does not support external_net_ns; skip the test
-		skip "this criu does not support external network namespaces"
-	fi
+	# Requires external network namespaces (criu >= 3.10).
+	requires criu_feature_external_net_ns
 
 	# create a temporary name for the test network namespace
 	tmp=$(mktemp)

tests/integration/helpers.bash

@@ -407,6 +407,12 @@ function requires() {
 				skip_me=1
 			fi
 			;;
+		criu_feature_*)
+			var=${var#criu_feature_}
+			if ! criu check --feature "$var"; then
+				skip "requires CRIU feature ${var}"
+			fi
+			;;
 		root)
 			if [ $EUID -ne 0 ]; then
 				skip_me=1