Rename contract! to contractadd! when α, β are specified

[mtfishman]

Also remove the version of contract accepting α (which was causing ambiguity errors) and rename unmatricize_add! to unmatricizeadd! to match the new naming convention of contractadd!.

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.82%. Comparing base (5873db1) to head (dbe4ee6).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
ext/TensorAlgebraTensorOperationsExt.jl	80.00%	1 Missing ⚠️
src/contract/contract.jl	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #82      +/-   ##
==========================================
+ Coverage   91.16%   92.82%   +1.66%     
==========================================
  Files          15       15              
  Lines         498      502       +4     
==========================================
+ Hits          454      466      +12     
+ Misses         44       36       -8     

Flag	Coverage Δ
docs	0.00% <0.00%> (ø)

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[mtfishman]

@ogauthe note the interface change, it might require some small updates to FusionTensors.jl.