When stack stats enabled, prevent exceptions if memory allocations fail

[davidsaada]

Description

Stack stats allocate memory for sending stat reports, usually based on number of threads. this may generate exceptions if not enough memory is available for this. Make sure this is handled properly.
Resolves #7712.

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Feature
[ ] Breaking change

[deepikabhavnani]

Thanks for the fix 👍

[davidsaada]

Please do not merge. Seems like I only solved part of the cases, but not all.

[davidsaada]

@cmonr @0xc0170 OK to merge. PR is good. The problem I found was in a specific test, which should be handled separately.

[adbridge]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2806
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7730/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2436
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7730/

[mbed-ci]

Test : SUCCESS

Build number : 2543
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7730/2543

[cmonr]

Holding for answer to question(s) about the new test-skipping behavior asked here: #7744 (review)

[davidsaada]

Holding for answer to question(s) about the new test-skipping behavior asked here: #7744 (review)

@cmonr I think we can move on, following our agreements in that PR.