[Backport 2.28] Add metatests for failing TEST_EQUAL and TEST_LE_*

[paul-elliott-arm]

Description

After getting caught with deadlock issues when these specific tests fail, add a metatest to test them failing.

This is a straight backport of #8829

PR checklist

Please tick as appropriate and edit the reasons (e.g.: "backport: not needed because this is a new feature")

• [ ] changelog ~~provided, or~~ not required (Test functionality only)
• [ ] backport ~~done, or~~ not required (This is the backport of #8829
• [ ] tests ~~provided, or~~ not required (part of test framework)