releng - uniform copyright/license headers

[kapilt]

Unifying copyright headers per cncf guidelines (https://github.com/cncf/foundation/blob/master/copyright-notices.md). Direct permission was obtained from corporate opensource offices for microsoft, amazon, and capital one. Direct permission was obtained from individual copyright holders, kapil thangavelu and karol lassak.

for clarification all code files in the repo should have the following header

# Copyright The Cloud Custodian Authors.                                                                                                                                                                                                                                                                                                                                                      
# SPDX-License-Identifier: Apache-2.0