chore: disallow relative imports

[bchampp]

Which issue(s) does this change fix?

Why is this change necessary?

Updating the linting configuration in SAM CLI to disallow relative imports.

How does it address the issue?

Adding updated rules in the linting configuration in pyproject.toml to disallow relative imports. Updating all instances of relative imports to absolute for make pr to pass.

What side effects does this change have?

None.

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• Review the generative AI contribution guidelines
• Add input/output type hints to new functions/methods
• Write design document if needed (Do I need to write a design document?)
• Write/update unit tests
• Write/update integration tests
• Write/update functional tests if needed
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.