Lock EASE solving to work around parallel bug

[mdekstrand]

Torch has a race condition initializing Choleseky solver, so this wraps our call to it in a lock.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.54%. Comparing base (e622c4e) to head (824faed).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1152   +/-   ##
=======================================
  Coverage   89.54%   89.54%           
=======================================
  Files         258      258           
  Lines       17313    17316    +3     
=======================================
+ Hits        15503    15506    +3     
  Misses       1810     1810           

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