rbd: add aws-sts-metdata encryption type

With Amazon STS and kubernetes cluster is configured with
OIDC identity provider, credentials to access Amazon KMS
can be fetched using oidc-token(serviceaccount token).
Each tenant/namespace needs to create a secret with aws region,
role and CMK ARN.
Ceph-CSI will assume the given role with oidc token and access
aws KMS, with given CMK to encrypt/decrypt DEK which will stored
in the image metdata.

Refer: https://docs.aws.amazon.com/STS/latest/APIReference/welcome.html
Resolves: #2879

Signed-off-by: Rakshith R <rar@redhat.com>

vendor/github.com/aws/smithy-go/io/byte.go

@@ -0,0 +1,12 @@
+package io
+
+const (
+	// Byte is 8 bits
+	Byte int64 = 1
+	// KibiByte (KiB) is 1024 Bytes
+	KibiByte = Byte * 1024
+	// MebiByte (MiB) is 1024 KiB
+	MebiByte = KibiByte * 1024
+	// GibiByte (GiB) is 1024 MiB
+	GibiByte = MebiByte * 1024
+)