[v2] Generate requirements lockfiles

[hssyoo]

Breakout PR of https://github.com/aws/aws-cli/pull/8757

To provide a stable build environment, this PR does the following:

• Move requirements.txt -> requirements-dev.txt to align with AWS CLI v1 and boto projects
• Alias requirements.txt to requirements-dev.txt for backwards compatibility
• Create a requirements-build-win.txt file as an extra source for pip-compile so lockfiles include Windows dependencies
• Extend regenerate-lock-files to generate lockfiles for base dependencies
• Generate lockfiles using regenerate-lock-files and replace their references in install scripts with requirements*-lock.txt
  • ./scripts/regenerate-lock-files --include-base --no-include-sdist
• Add a test to ensure lockfiles generated with pyproject.toml as an input have version pins that are within the bounds set in pyproject.toml
  • This test ensures that if a dependency version range is updated in pyproject.toml, the lockfiles are also updated