make all datetime factories consistent to use utcnow func in utils

[tsmathis]

split out housekeeping changes introduced in #1243 to reduce noise in diffs

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.66667% with 7 lines in your changes missing coverage. Please review.

Project coverage is 89.55%. Comparing base (fb4fa77) to head (7635206).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
emmet-core/emmet/core/common.py	76.47%	4 Missing ⚠️
emmet-core/emmet/core/electronic_structure.py	81.81%	2 Missing ⚠️
emmet-core/emmet/core/vasp/validation.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1245      +/-   ##
==========================================
- Coverage   89.56%   89.55%   -0.01%     
==========================================
  Files         150      150              
  Lines       15319    15368      +49     
==========================================
+ Hits        13720    13763      +43     
- Misses       1599     1605       +6     

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