• 
  Could this introduce any breaking changes? If yes, please explain.

No.

• 
  What is the risk and potential customer impact of backporting this?

Low risk. This enables more testing because bsoncolumn_test.cpp is not compiling on v8.0.

• 
  If the risk is not low, then what would a smaller and simpler solution or mitigation to this issue be? (assuming leaving the issue unfixed is also not low impact). For example, see the comments in BACKPORT-5428 and its CR.

N/A, low risk.

• 
  What is the risk and potential customer impact of not backporting this?

We will not have coverage of bsoncolumn_test.cpp on v8.0.

• 
  Why is it worth the risk to backport?

This will provide test coverage for bsoncolumn on v8.0