[Gen 3] LittleFS truncate fix (https://github.com/littlefs-project/littlefs/issues/268)

[avtolstoy]

Problem

See littlefs-project/littlefs#268

Solution

1. Use patch from the above PR.
2. Add stress test to wiring/filesystem test suite. It fails without the patch on checking the integrity of the data after a truncate, it works fine with the patch.
3. (Minor and unrelated) Use .balign instead of .align in inline assembly, as .align X on ARM platforms semantically means 2^X alignment (and on other platforms it's just X alignment). .balign always means X alignment.

Steps to Test

• wiring/filesystem built out of this branch with 3.2.0-rc.1, wiring/filesystem with system-part built out of this branch

Example App

N/A

References

• [SC93531]

---

Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)