SKIP UPDATE CHECK: Added Integration testing steps to DEVELOPMENT_MAINTENANCE.md

General MR

Summary

Update the docs/DEVELOPMENT_MAINTENANCE.md docs with a # Files That Require Integration Testing. For the definition of those, see the epic description. Ensure to include the instructions on how to run integration tests.

Relevant logs/screenshots

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Linked Issue

Closes big-bang/bigbang#2129 (closed)

Upgrade Notices

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