Merge pull request #49300 from tklauser/syscall-to-x-sys-unix

Automatic merge from submit-queue

Switch from package syscall to golang.org/x/sys/unix

**What this PR does / why we need it**:

The syscall package is locked down and the comment in https://github.com/golang/go/blob/master/src/syscall/syscall.go#L21-L24 advises to switch code to use the corresponding package from golang.org/x/sys. This PR does so and replaces usage of package syscall with package golang.org/x/sys/unix where applicable. This will also allow to get updates and fixes
without having to use a new go version.

In order to get the latest functionality, golang.org/x/sys/ is re-vendored. This also allows to use Eventfd() from this package instead of calling the eventfd() C function.

**Special notes for your reviewer**:

This follows previous works in other Go projects, see e.g. moby/moby#33399, cilium/cilium#588

**Release note**:

```release-note
NONE
```

pkg/proxy/userspace/BUILD

@@ -28,6 +28,7 @@ go_library(
         "//pkg/util/iptables:go_default_library",
         "//pkg/util/slice:go_default_library",
         "//vendor/github.com/golang/glog:go_default_library",
+        "//vendor/golang.org/x/sys/unix:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/types:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/errors:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/net:go_default_library",

pkg/proxy/userspace/rlimit.go

@@ -18,8 +18,8 @@ limitations under the License.
 
 package userspace
 
-import "syscall"
+import "golang.org/x/sys/unix"
 
 func setRLimit(limit uint64) error {
-	return syscall.Setrlimit(syscall.RLIMIT_NOFILE, &syscall.Rlimit{Max: limit, Cur: limit})
+	return unix.Setrlimit(unix.RLIMIT_NOFILE, &unix.Rlimit{Max: limit, Cur: limit})
 }