Adding `constants.py` and integrating it into AE

[claalmve]

Description of PR

Summary of changes and related issue

Introducing a constants.py file in AE that can house a variety of constants we define across the codebase. The first constant introduced in this PR is WARMING_LEVELS = [0.8, 1.2, 1.5, 2.0, 3.0, 4.0], and it's integration into places of the codebase (where appropriate) are detailed within this PR.

Relevant motivation and context

We want to reduce the number of hard-coded definitions of 'constants' around the codebase, so that when one gets changed, the others can all follow suit easily.

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Definition of Done Checklist

Practical

• [ ] 80% unit test coverage
• [ ] Documentation
  • [ ] All functions/adjusted functions documented in the readthedocs.
  • [ ] Documentation is pushed
• [x] Complex code commented
• [x] Naming conventions followed
  • [ ] Helper functions hidden with _ before the name
• [x] Context of function is clearly provided
  • [ ] Intent of function is provided
  • [ ] How to test, so that it is not siloed on scientists and anyone can review
  • [ ] Appropriate manual testing was completed
• [x] Any notebooks known to utilize the affected functions are still working
• [x] Linting completed and resolved

Conceptual

• [x] Doesn't replicate existing functionality
• [x] Aligns with general coding standard of existing functions
• [x] Matches desired functionality from users/scientists