TEST: update usb tests and guard them with macro

[jamesbeyond]

Summary of changes

Some feedback we received recently: the USB devices tests are quite different from the rest of the greentea tests.

• They are not like other Greentea tests works straightaway
• Silicon partners need to read through the README file and implement a series of local configurations before running the tests
• 2 USB cables need to be physically plugged into to host, instead of one
• There are some known limitations already some tests won't work with some platforms

So we decided to guard those tests with a macro. when silicon partners want to port the USB devices, he will need to follow the README instructions. and then run the tests.

Impact of changes

Migration actions required

Documentation

Updates included

---

Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

---

Test results

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

---

Reviewers

@MarceloSalazar @fkjagodzinski @maciejbocianski

---

[MarceloSalazar]

FYI @ARMmbed/team-st-mcd

[maciejbocianski]

Lack of new line at the file end, Applies to all files

[jamesbeyond]

fixed

[ciarmcom]

@jamesbeyond, thank you for your changes.
@maciejbocianski @fkjagodzinski @MarceloSalazar @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

Fix the missing new line at the end of the line.

Is this "exclude" the way we want to use? greentea does not support something similar to --exclude usb-* - wouldn't this be preferable ?

Pull request has been modified.

[jamesbeyond]

Fix the missing new line at the end of the line.

Fixed, Could you remind why we need this empty line? @0xc0170, I remember it is in the contributions requirement, but can't recall why

Is this "exclude" the way we want to use? greentea does not support something similar to --exclude usb-* - wouldn't this be preferable ?

Greentea has an excluding method. but it command line will end up too long if we excluding too many things.
Base on the feedback from @MarceloSalazar, I think partners turn to use greentea without any excluding options, which those tests end up failing because of local configurations. Also I agree that using the macro would be a benefit for both CI and partners

[0xc0170]

Fixed, Could you remind why we need this empty line? @0xc0170, I remember it is in the contributions requirement, but can't recall why

at least uvision prints a warning , and possibly some other but dont recall any other. We always keep one line empty since the beginning.

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 5 of 5 test jobs passed
Build number : 1
Build artifacts