Reactivate block device tests

[multiplemonomials]

Summary of changes

This PR reactivates the tests of all the block devices under storage/blockdevices, Looking at these tests initially I had thought that they were just for the "software" block devices like SlicingBlockDevice, but actually no: the "general" block device test actually tests all the hardware block device drivers if they exist on the current target.

I set up the build system for these tests so that they should now be able to run again.

Impact of changes

Migration actions required

Documentation

None

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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)

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Test results

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

I ran the new tests on Arduino Giga (which has a QSPIF block device) and they all passed.

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Reviewers

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[multiplemonomials]

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