mlkem: initial implementation (#119)

* mlkem: initial implementation

* quim fixes

* fixup and add tests

* only store raw key in types

* deduplicate code

* remove allocation

* Apply suggestions from code review

Co-authored-by: Quim Muntal <qmuntaldiaz@microsoft.com>

* refactor newMLKEMEncapsulationKeyFromBytes

* return err in all cases

---------

Co-authored-by: Quim Muntal <qmuntaldiaz@microsoft.com>

Author: gdams

cng/export_test.go

@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+//go:build windows
+// +build windows
+
+package cng
+
+// MLKEM constants for testing against the stdlib
+var (
+	SharedKeySizeMLKEM            = sharedKeySizeMLKEM
+	SeedSizeMLKEM                 = seedSizeMLKEM
+	CiphertextSizeMLKEM768        = ciphertextSizeMLKEM768
+	EncapsulationKeySizeMLKEM768  = encapsulationKeySizeMLKEM768
+	CiphertextSizeMLKEM1024       = ciphertextSizeMLKEM1024
+	EncapsulationKeySizeMLKEM1024 = encapsulationKeySizeMLKEM1024
+)