Fix CTMRG contraction inconsistencies

[pbrehmer]

As pointed out in #325, there are multiple inconsistencies in the docstrings, index labels and names of the CTMRG contraction code. Here I fix the docstrings, call all projectors either P_left or P_right corresponding to left and right isometries, respectively, and relabel the indices as in and out-going consistently with the TensorKit conventions.

[codecov]

Codecov Report

❌ Patch coverage is 40.00000% with 36 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../algorithms/contractions/ctmrg/renormalize_edge.jl	35.00%	13 Missing ⚠️
...lgorithms/contractions/ctmrg/renormalize_corner.jl	52.38%	10 Missing ⚠️
src/algorithms/contractions/ctmrg/fullinf_env.jl	0.00%	4 Missing ⚠️
src/algorithms/contractions/ctmrg/halfinf_env.jl	0.00%	4 Missing ⚠️
src/algorithms/contractions/ctmrg/projector.jl	0.00%	4 Missing ⚠️
src/algorithms/contractions/ctmrg/gaugefix.jl	80.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
...rc/algorithms/contractions/ctmrg/enlarge_corner.jl	65.00% <ø> (ø)
src/algorithms/ctmrg/sequential.jl	98.41% <100.00%> (ø)
src/algorithms/contractions/ctmrg/gaugefix.jl	95.45% <80.00%> (ø)
src/algorithms/contractions/ctmrg/fullinf_env.jl	2.89% <0.00%> (ø)
src/algorithms/contractions/ctmrg/halfinf_env.jl	6.81% <0.00%> (ø)
src/algorithms/contractions/ctmrg/projector.jl	38.46% <0.00%> (ø)
...lgorithms/contractions/ctmrg/renormalize_corner.jl	43.85% <52.38%> (ø)
.../algorithms/contractions/ctmrg/renormalize_edge.jl	65.88% <35.00%> (ø)

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