Avoid allocating a String when hashing a lazy tensor

[mtfishman]

Summary

Makes hashing a lazy tensor allocation-free. hash_lazy built its type discriminator with Symbol(Base.typename(typeof(a)).wrapper), and Symbol has no method taking a type, so it fell back to rendering the type through an IOBuffer on every call. nameof gives the same discriminator as a Symbol for free.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.92%. Comparing base (6a051bd) to head (d72674f).

Additional details and impacted files

@@               Coverage Diff                @@
##           release-0.13     #253      +/-   ##
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+ Coverage         77.37%   77.92%   +0.55%     
================================================
  Files                30       30              
  Lines              1812     1812              
================================================
+ Hits               1402     1412      +10     
+ Misses              410      400      -10     

Flag	Coverage Δ
docs	26.30% <0.00%> (?)

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