chore: add/update copyright headers to all files and add CI to check and enforce headers and formatting

Similar to https://github.com/awslabs/aws-encryption-sdk-specification/blob/master/.github/workflows/ci_static-analysis.yaml and https://github.com/awslabs/aws-encryption-sdk-specification/blob/master/.github/not-grep.toml

- [ ] prettify all files
- [ ] add prettier CI check
- [ ] add/update copyright headers on all files
- [ ] add not-grep CI check for copyright headers

Start by reviewing the repository's file tree and comparing the referenced ci_static-analysis.yaml and .github/not-grep.toml examples. Determine the formatting and copyright-header rules for each file type, then verify that all files are formatted and that CI checks and enforces the headers and formatting.

Written by the indexing model from the issue text.