Fix bug in linter interactive mode, and final improvements

[aemous]

Description of changes:

• Added copyright header to all source files.
• Created new Legal Notices file.
• Created empty CHANGELOG.md file, which will be appended in future releases.
• Changed project name to aws-cli-migrate and package name to aws_cli_migrate.
• Made output between interactive mode and auto-output mode more consistent where possible.
• Fix bug in interactive mode where subsequent rules were not updating the AST, leading to auto-fixes to be missed.
• Improved testing, including a new regression test for the interactive-mode bug described above.
• Added IDEA IDE files to .gitignore.
• Explicitly add Python 3.13 as a supported version in pyproject.toml.
• Updated LICENSE to match guidance.
• Misc. refactoring for maintainability and readability.
• Misc. changes to README.md file.

Description of tests:

• Ran and passed all tests and linters.
• Ran manual testing using example scripts.

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[hssyoo]

Looks fine, just had a couple small comments.

In the future we should break these kind of PRs out into 3 separate PRs:

1. License/changelog updates
2. Logical changes
3. Refactoring/cleaning up

[aemous]

In the future we should break these kind of PRs out into 3 separate PRs:

Will do, thank you.