[Core] Zero size memory quick returns

[noelchalmers]

Description

Let some memory methods return quickly instead of error when they are zero size allocations.

Addresses #648, but in a different manner than PR #649.

@MalachiTimothyPhillips can you weight in if this would solve your issue?

[codecov]

Codecov Report

Merging #678 (9398b6c) into development (cbdd074) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 9398b6c differs from pull request most recent head 459ed52. Consider uploading reports for the commit 459ed52 to get more accurate results

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #678      +/-   ##
===============================================
- Coverage        76.23%   76.22%   -0.01%     
===============================================
  Files              291      291              
  Lines            18798    18795       -3     
===============================================
- Hits             14330    14326       -4     
- Misses            4468     4469       +1     

Impacted Files	Coverage Δ
src/core/memory.cpp	83.33% <100.00%> (-0.12%)	⬇️

... and 2 files with indirect coverage changes

[kris-rowe]

Since these changes were included in nekRS after this PR was opened, I am going to assume that this solution works for them.