Add support for SSE-S3 server side encryption with vault (#6192)

Add support for sse-s3 encryption with vault as KMS.

Also refactoring code to make use of headers and functions defined in
crypto package and clean up duplicated code.

vendor/github.com/hashicorp/hcl/hcl.go

@@ -0,0 +1,11 @@
+// Package hcl decodes HCL into usable Go structures.
+//
+// hcl input can come in either pure HCL format or JSON format.
+// It can be parsed into an AST, and then decoded into a structure,
+// or it can be decoded directly from a string into a structure.
+//
+// If you choose to parse HCL into a raw AST, the benefit is that you
+// can write custom visitor implementations to implement custom
+// semantic checks. By default, HCL does not perform any semantic
+// checks.
+package hcl