Updated the repositories to comply with the current copyright best practices

* https://opensource.google/docs/releasing/preparing/#license-headers
* https://opensource.google/docs/releasing/authors/

Specific things that need to be done;
- [ ] `COPYING` file renamed to `LICENSE` file
- [ ] The `LICENSE` file should start with - `Copyright 20XX The [Project Name] Authors.` -- See https://opensource.google/docs/releasing/authors/
- [ ] The default should be `SymbiFlow Authors` isn't specialized below.
- [ ] Project X-Ray --> `The Project X-Ray Authors`
- [ ] Project U-Ray --> `The Project U-Ray Authors`
- [ ] Project Trellis --> `The Project Trellis Authors`
- [ ] Add or update the `AUTHORS` files to have the text as shown at https://opensource.google/docs/releasing/authors/
- [ ] Remove the un-needed `All rights reserved.` text.
- [ ] Make sure all code files have the license specifier at the top of the file as shown at https://opensource.google/docs/releasing/licenses/
- [ ] All code files should have `SPDX` identifiers.
- [ ] Add CI which checks for all this.
- [ ] Make sure that all `third_party` code is under `third_party` directory.
- [ ] Make sure that all `third_party` directories have a correct `LICENSE` file.
- [ ] Python files should have a `#!/usr/bin/env python3` as the shebang line.
- [ ] Python files should have a `# coding: utf-8` as the second line after the shebang.

What other things are missing?