Cached workspace prototype for custatevec

[kshyatt]

Attempt to attach a buffer to each library handle so we can re-use the buffers for many small calls to the same handle and avoid thrashing GC.

[codecov]

Codecov Report

Attention: Patch coverage is 89.92248% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 72.02%. Comparing base (2783c88) to head (aefb38d).

Files	Patch %	Lines
lib/cusparse/generic.jl	84.74%	9 Missing ⚠️
lib/utils/call.jl	90.90%	2 Missing ⚠️
lib/custatevec/src/cuStateVec.jl	85.71%	1 Missing ⚠️
lib/custatevec/src/statevec.jl	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2279      +/-   ##
==========================================
+ Coverage   72.00%   72.02%   +0.02%     
==========================================
  Files         155      155              
  Lines       14862    14881      +19     
==========================================
+ Hits        10701    10718      +17     
- Misses       4161     4163       +2     

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[maleadt]

This is probably something useful we could apply to other libraries too.

[kshyatt]

Fixed all except adding to with_workspace -- are we all on board with introducing this there as well?

[maleadt]

Alright, this looks nice. We could probably apply this pattern to more libraries, but let's merge this already.