support cgroup2

* only shim v2 runc v2 ("io.containerd.runc.v2") is supported
* only PID metrics is implemented. Others should be implemented in separate PRs.
* lots of code duplication in v1 metrics and v2 metrics. Dedupe should be separate PR.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/github.com/cilium/ebpf/internal/endian.go

@@ -0,0 +1,24 @@
+package internal
+
+import (
+	"encoding/binary"
+	"unsafe"
+)
+
+// NativeEndian is set to either binary.BigEndian or binary.LittleEndian,
+// depending on the host's endianness.
+var NativeEndian binary.ByteOrder
+
+func init() {
+	if isBigEndian() {
+		NativeEndian = binary.BigEndian
+	} else {
+		NativeEndian = binary.LittleEndian
+	}
+}
+
+func isBigEndian() (ret bool) {
+	i := int(0x1)
+	bs := (*[int(unsafe.Sizeof(i))]byte)(unsafe.Pointer(&i))
+	return bs[0] == 0
+}