test(NODE-6017): add an s390x big endian test

[nbbeeken]

Description

What is changing?

• Add a zSeries task that specifically runs the big endian test
• Temporary solution to make sure our change actually fixes the bug and no further regressions

Is there new documentation needed for these changes?

No.

What is the motivation for this change?

• Inspect what we expect

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[nbbeeken]

• Failing before fix merged
• Succeeding after fix merged