Allow ULID for MPIDS

[jmmshn]

Following the discussion here:
materialsproject/jobflow#519

Added support for ULID: Universally Unique Lexicographically Sortable Identifier

The idea is the UUIDs are random and they cannot be sorted for aggregate document creation.
Since atomate2 will call some emmet.core documents directly we might not always have a chance to parse the task docs and assign MPIDs to everyone.

This PR does the following:

1. Allows ULID to be used to as MPIDS
2. The self.parts used for sorting are (ULID_ID, 0) which should enough to help sort the documents.
3. Updated the logic in StructureGroup to allow for ULID comparison.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (4372799) 90.54% compared to head (b8be354) 88.88%.

Files	Patch %	Lines
emmet-core/emmet/core/mpid.py	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #928      +/-   ##
==========================================
- Coverage   90.54%   88.88%   -1.67%     
==========================================
  Files         139      109      -30     
  Lines       13203    10054    -3149     
==========================================
- Hits        11955     8936    -3019     
+ Misses       1248     1118     -130     

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