Update headers in src files

[rschwant]

We need to update the headers in all the src files to remove this line:
"# Copyright (C) 2022 National Center for Atmospheric Research and National Oceanic and Atmospheric Administration"

Update the checks to only check for this line on top of all source code files instead of both lines
"# SPDX-License-Identifier: Apache-2.0"

And then add a NOTICE file and copy the copyright above there instead. Then we don't have separate copyright dates for new pieces of code and we do not have to update these headers every year to add in 2022 - 2024 etc.

Since we are just moving this notice to one location, no copyright changes to the code occur. This is just restructuring and aligns us with how the apache license recommends you set up your repository here: https://infra.apache.org/licensing-howto.html

Let's do this in the lull after we close out our current PRs after conferences and before winter break since this will result in changes to a lot of files and I don't want to cause merge conflicts. @blychs can you merge your TEMPO updates in without updating this for now and we will fix this after AGU? Or do we need to fix this before your PR goes through?