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/encoding/encoding.go

@@ -0,0 +1,40 @@
+package encoding
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+)
+
+// EncodeFloat encodes a float value as per the stdlib encoder for json and xml protocol
+// This encodes a float value into dst while attempting to conform to ES6 ToString for Numbers
+//
+// Based on encoding/json floatEncoder from the Go Standard Library
+// https://golang.org/src/encoding/json/encode.go
+func EncodeFloat(dst []byte, v float64, bits int) []byte {
+	if math.IsInf(v, 0) || math.IsNaN(v) {
+		panic(fmt.Sprintf("invalid float value: %s", strconv.FormatFloat(v, 'g', -1, bits)))
+	}
+
+	abs := math.Abs(v)
+	fmt := byte('f')
+
+	if abs != 0 {
+		if bits == 64 && (abs < 1e-6 || abs >= 1e21) || bits == 32 && (float32(abs) < 1e-6 || float32(abs) >= 1e21) {
+			fmt = 'e'
+		}
+	}
+
+	dst = strconv.AppendFloat(dst, v, fmt, -1, bits)
+
+	if fmt == 'e' {
+		// clean up e-09 to e-9
+		n := len(dst)
+		if n >= 4 && dst[n-4] == 'e' && dst[n-3] == '-' && dst[n-2] == '0' {
+			dst[n-2] = dst[n-1]
+			dst = dst[:n-1]
+		}
+	}
+
+	return dst
+}