Add some basic support for svd_trunc_no_error

[kshyatt]

My goal here is to start allowing users to set in the algorithm whether or not they want the truncation error computed. The benefit of not computing it is increased speed and possibly some AD benefits. For now I've done the easiest part -- hooking up svd_trunc_no_error, adding ChainRules.jl pullback support, and adding tests. Next is to figure out a nice way to control when to use it in the actual CTMRG functions themselves.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 63 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/utility/svd.jl	0.00%	63 Missing ⚠️

Files with missing lines	Coverage Δ
src/utility/svd.jl	8.86% <0.00%> (-43.19%)	⬇️

... and 59 files with indirect coverage changes

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[github-actions]

Your PR no longer requires formatting changes. Thank you for your contribution!

[pbrehmer]

Looks good to me, thanks! I'm curious though, is there a specific use case that we had in mind where we need this SVD without computing the truncation error? I guess you already mentioned increased performance so that's already a good reason :-)

[kshyatt]

It might be nice to not have to calculate it every time for the GPUified PEPS as computing the error is actually surprisingly expensive.