Static Type Checking Intro

[mrm9084]

Description

This PR starts to add static type checking to the Feature Management library.
See: mypy.ini for details on what is enabled and what isn't.

Starts work on this: #33

Note: Currently this will not be part of the build step until more is done.
Note: Due to some of the type check added to pass mypy some code changes were required.

Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.
• Pull request includes test coverage for the included changes.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR.

[rossgrambo]

Feels weird to pass in the name here only for the error message.

[mrm9084]

This is so we can match the error message as we have in the other libraries. It also feels weird to do the check outside of this.