build: move e2e dependencies into e2e/go.mod

Several packages are only used while running the e2e suite. These
packages are less important to update, as the they can not influence the
final executable that is part of the Ceph-CSI container-image.

By moving these dependencies out of the main Ceph-CSI go.mod, it is
easier to identify if a reported CVE affects Ceph-CSI, or only the
testing (like most of the Kubernetes CVEs).

Signed-off-by: Niels de Vos <ndevos@ibm.com>

e2e/vendor/github.com/josharian/intern/intern.go

@@ -0,0 +1,44 @@
+// Package intern interns strings.
+// Interning is best effort only.
+// Interned strings may be removed automatically
+// at any time without notification.
+// All functions may be called concurrently
+// with themselves and each other.
+package intern
+
+import "sync"
+
+var (
+	pool sync.Pool = sync.Pool{
+		New: func() interface{} {
+			return make(map[string]string)
+		},
+	}
+)
+
+// String returns s, interned.
+func String(s string) string {
+	m := pool.Get().(map[string]string)
+	c, ok := m[s]
+	if ok {
+		pool.Put(m)
+		return c
+	}
+	m[s] = s
+	pool.Put(m)
+	return s
+}
+
+// Bytes returns b converted to a string, interned.
+func Bytes(b []byte) string {
+	m := pool.Get().(map[string]string)
+	c, ok := m[string(b)]
+	if ok {
+		pool.Put(m)
+		return c
+	}
+	s := string(b)
+	m[s] = s
+	pool.Put(m)
+	return s
+}