Feature iar8 rebase - Storage test fix

[deepikabhavnani]

Description

DO NOT MERGE

Commit - f7a6d25 is added on top of feature-iar8 rebase PR #9811

Random number generation API's - rand() and srand() are made sparse to not have same block.

Failure was noted when 2 threads getting same random number were trying to write to same block and rechecking resulted in error (since block was over-written by another thread).

Instead of checking the same random data written, checksum logic can be used in future. Threads are allowed to overwrite the data (block commands are not in mutex) in test, so instead of verifying the exact data some checksum of data should be checked to make sure data was not jumbled up 2-threads accessing it.

Pull request type

[] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Reviewers

@ARMmbed/mbed-os-storage

[deepikabhavnani]

Started CI to check the fix

[mbed-ci]

Test run: SUCCESS

Summary: 6 of 6 test jobs passed
Build number : 1
Build artifacts

[0xc0170]

As this is targeting feature iar8 and the fix for storage is separate , this shall be good to go and the fix will be taken separately (feature iar8 still needs some work).

[NirSonnenschein]

pushed to branch