Legal has approved replacing our current 28 line header comment with:

// Copyright (c) MongoDB, Inc.
// SPDX-License-Identifier: SSPL-1.0

This also removes the year, which was frequently forgotten about when copy-pasting to a new file.

Plan of attack with a week or so between steps to minimize disruption of in-progress PRs, and avoid mixing real changes that need to be reviewed with wide, mechanical ones:

1. Update the license check in mongolint.py to support both forms, and update code generators to use the new one. (Announce the change as soon as this lands and tell people to use the new form in new code)
2. Use a script to bulk-update all source files to use the new license. (This will probably be the only break-glass commit)
3. Remove the old form from mongolint.py and rerun the script to pick up any stragglers.