string: strerror_r() implementation

[agkaminski]

DONE: RTOS-554

Description

Fixes phoenix-rtos/phoenix-rtos-project#694

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: (ia32-generic-qemu).

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[mateusz-bloch]

LGTM, checked strerror_r on emu and hardware targets

[badochov]

strerror should only have race with itself, but in current implementation there's a race between strerror and gai_strerror, I'd make err_unknownMsg a static variable inside each of this functions

[badochov]

I've never seen those failures on imxrt117 before however the code seems valid

[agkaminski]

I've never seen those failures on imxrt117 before however the code seems valid

Random fail yet again

[badochov]

LGTM