container/bits: move bind bits

This allows referring to the bits without importing container.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/bits/bits.go

@@ -0,0 +1,13 @@
+// Package bits contains constants for configuring the container.
+package bits
+
+const (
+	// BindOptional skips nonexistent host paths.
+	BindOptional = 1 << iota
+	// BindWritable mounts filesystem read-write.
+	BindWritable
+	// BindDevice allows access to devices (special files) on this filesystem.
+	BindDevice
+	// BindEnsure attempts to create the host path if it does not exist.
+	BindEnsure
+)