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/aws-sdk-go-v2/internal/strings/strings.go

@@ -0,0 +1,11 @@
+package strings
+
+import (
+	"strings"
+)
+
+// HasPrefixFold tests whether the string s begins with prefix, interpreted as UTF-8 strings,
+// under Unicode case-folding.
+func HasPrefixFold(s, prefix string) bool {
+	return len(s) >= len(prefix) && strings.EqualFold(s[0:len(prefix)], prefix)
+}