Add local preconditioner

[leburgel]

Adds a local preconditioner for variational PEPS optimization, enabled by default.

Requires #410.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 7 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/algorithms/optimization/preconditioning.jl	85.71%	3 Missing ⚠️
src/algorithms/select_algorithm.jl	92.00%	2 Missing ⚠️
src/algorithms/optimization/peps_optimization.jl	96.42%	1 Missing ⚠️
src/states/infinitepeps.jl	50.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/Defaults.jl	85.71% <ø> (ø)
...rithms/optimization/fixed_point_differentiation.jl	85.47% <100.00%> (-3.33%)	⬇️
src/algorithms/optimization/peps_optimization.jl	95.83% <96.42%> (+1.09%)	⬆️
src/states/infinitepeps.jl	67.52% <50.00%> (+0.56%)	⬆️
src/algorithms/select_algorithm.jl	82.60% <92.00%> (+5.68%)	⬆️
src/algorithms/optimization/preconditioning.jl	85.71% <85.71%> (ø)

... and 4 files with indirect coverage changes

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