Fix `hcat` function to handle label replacement in tensor networks correctly

[jofrevalles]

This pull request addresses the issue encountered (resolves #64) when computing the norm of a Matrix Product Operator (MPO).

The problem arises when the function attempts to replace a tensor label in a tensor network with a new one that already exists. This scenario often occurs with MPOs and other tensor structures with multiple interlayer connections, as the plug labels might not be in the same order in the state and its adjoint.

This error was not encountered with Matrix Product States (MPS) because they have a single interlayer that matches their adjoint.

In this PR we have corrected this error and we also have introduced tests to validate the norm function for both MPS and MPO.

[codecov[bot]]

Codecov Report

Merging #66 (18c3a0e) into master (05a2bae) will increase coverage by 4.00%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
+ Coverage   84.97%   88.98%   +4.00%     
==========================================
  Files           9        9              
  Lines         599      599              
==========================================
+ Hits          509      533      +24     
+ Misses         90       66      -24     

Impacted Files	Coverage Δ
src/Quantum/Quantum.jl	78.94% <100.00%> (+3.15%)	:arrow_up:

... and 1 file with indirect coverage changes