[WIP] Strict typing and fixed schemas for emmet document models

[esoteric-ephemera]

The goal of this PR is to make fixed, (more-)explicitly typed document models for storing tasks / converting python objects to parquet. To do this, we have to:

• Make document models for some specific pymatgen objects (POTCAR summary stats, ComputedEntry, etc.)
• Make a strict schema (not permitting extra model fields and no union types on fields besides Optional) for TaskDoc
• Maybe concurrent: pydantic models that are low-memory implementations of objects like Structure, PeriodicSite, etc.

To avoid breaking changes, TaskDoc is the same as before, but inherits from a DbTaskDoc which meets the strict criteria above

Other concurrent goals:

• Better PEP585 compliance by partially migrating away from type hints based on the typing package

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.15924% with 39 lines in your changes missing coverage. Please review.

Project coverage is 71.92%. Comparing base (a1b5ff2) to head (c9b4871).

Files with missing lines	Patch %	Lines
emmet-core/emmet/core/tasks.py	64.64%	35 Missing ⚠️
emmet-core/emmet/core/vasp/calculation.py	90.47%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1174      +/-   ##
==========================================
- Coverage   72.13%   71.92%   -0.21%     
==========================================
  Files          77       77              
  Lines        5149     5196      +47     
==========================================
+ Hits         3714     3737      +23     
- Misses       1435     1459      +24     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.