Fix minimal-printf stack overflow

[evedon]

Summary of changes

In nightly test, mbed-os-example-crash-reporting fails on GCC_ARM when linking with minimal-printf due to a stack overflow. The fix is to allocate the two int2hex arrays in mbed_minimal_formatted_string_hexadecimal from the heap instead of the stack.

The test now passes although the amount of stack left in the main thread is minimal.

This is the crash reporting Mbed OS example
1st run: Inject the fault exception

++ MbedOS Fault Handler ++

FaultType: HardFault

(...)
-- MbedOS Fault Handler --

++ MbedOS Error Info ++
Error Status: 0x80FF013D Code: 317 Module: 255
Error Message: Fault exception
Location: 0xE64
Error Value: 0x1FFF0400
Current Thread: main Id: 0x20000E74 Entry: 0x2DC7 StackSize: 0x1000 StackMem: 0x20001E60 SP: 0x20002E38

Impact of changes

Fix mbed-os-example-crash-reporting nightly test.

Migration actions required

None

Documentation

N/A

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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)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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[ciarmcom]

@evedon, thank you for your changes.
@ARMmbed/mbed-os-core @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

Please fix the style (see astyle failures)

[evedon]

astyle issue fixed.

[0xc0170]

CI started

[mbed-ci]

Test run: FAILED

Summary: 1 of 8 test jobs failed
Build number : 1
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_cloud-client-pytest

[evedon]

@0xc0170 Can you restart CI for cloud-client-test please as I don't think it is related to my PR?

[0xc0170]

I restarted the client test. There is an issue somewhere, reported few days back. I am trying to find out the status today as it has been still failing recently

[0xc0170]

Client restarted

[0xc0170]

Restarted again, the test was disabled until its fixed, tracked internally.