Create stats compare endpoint to compare two summaries CRASM-2584

[DJensen94]

🗣 Description

Create new endpoint that will compare summaries from two provided dates. The comparison will provide count deltas and percentage deltas as well as the full summary of the two dates

💭 Motivation and context

This endpoint will be used to show changes overtime for vs dashboard statistics. This will let stakeholders track changes to their attack surface over time.

🧪 Testing

Tested locally and via pytests

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

[rapidray12]

THe code is fine but we will need to work on accompanying documentation