Added kv store adaptation to nanostack file interface

[mikaleppanen]

Summary of changes

This is port of #12878 to Mbed OS master.

Added NS filesystem API module to mbed-os Nanostack HAL. Module provides kv_store interface for the Nanostack. Feature is disabled by default on .json configuration.

Impact of changes

None

Migration actions required

None

Documentation

None

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Pull request type

[] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[X] 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

@mikter @artokin @juhhei01 @JarkkoPaso

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[0xc0170]

Same as another PR, lets try to rebase to clean up the psa error (there were some removals on master recently)

Pull request has been modified.

[mikaleppanen]

@0xc0170 Rebased over latest master.

[adbridge]

@0xc0170 @mikter could you guys please re-review this?

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 7 of 7 test jobs passed
Build number : 1
Build artifacts