Replace instance_idx with leader leasing

[tokebe]

Fixes a bug which causes multiple instances to fail at building subclass mapping

[codecov]

Codecov Report

❌ Patch coverage is 70.77922% with 45 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/retriever/utils/redis.py	44.00%	14 Missing ⚠️
src/retriever/metadata/optable.py	27.27%	8 Missing ⚠️
src/retriever/utils/leader.py	91.48%	4 Missing and 4 partials ⚠️
src/retriever/lookup/subclass.py	40.00%	6 Missing ⚠️
src/retriever/background.py	0.00%	5 Missing ⚠️
src/retriever/status.py	0.00%	4 Missing ⚠️

Files with missing lines	Coverage Δ
src/retriever/config/general.py	96.24% <100.00%> (ø)
src/retriever/types/status.py	100.00% <100.00%> (ø)
src/retriever/status.py	26.64% <0.00%> (-0.38%)	⬇️
src/retriever/background.py	0.00% <0.00%> (ø)
src/retriever/lookup/subclass.py	44.13% <40.00%> (-0.55%)	⬇️
src/retriever/metadata/optable.py	20.42% <27.27%> (+0.15%)	⬆️
src/retriever/utils/leader.py	91.48% <91.48%> (ø)
src/retriever/utils/redis.py	42.50% <44.00%> (+0.46%)	⬆️

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