Update integration testing explainer docs to better outline our system

[jlarson4]

Description

Improving documentation around how best to integration test our architecture adapters, specifically those that run larger models.

Type of change

• This change requires a documentation update

Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have not rewritten tests relating to key interfaces which would affect backward compatibility