Update process_nodes to use new format of schema cache

[ogenstad]

This PR fixes a bug uncovered by opsmill/infrahub#6112

A test pipeline to validate against the Infrahub repo can be found here:
opsmill/infrahub#6115

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
infrahub_sdk/generator.py	0.00%	1 Missing ⚠️

@@           Coverage Diff           @@
##           stable     #317   +/-   ##
=======================================
  Coverage   71.32%   71.32%           
=======================================
  Files          87       87           
  Lines        7871     7871           
  Branches     1517     1517           
=======================================
  Hits         5614     5614           
  Misses       1865     1865           
  Partials      392      392           

Flag	Coverage Δ
integration-tests	22.80% <0.00%> (ø)
python-3.10	45.48% <0.00%> (+0.02%)	⬆️
python-3.11	45.48% <0.00%> (+0.02%)	⬆️
python-3.12	45.45% <0.00%> (ø)
python-3.13	45.45% <0.00%> (-0.03%)	⬇️
python-3.9	44.37% <0.00%> (+0.02%)	⬆️
python-filler-3.12	24.66% <0.00%> (ø)

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Files with missing lines	Coverage Δ
infrahub_sdk/generator.py	35.44% <0.00%> (ø)

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