Add #greaseAsByteArray and implementation for Squeak

[theseion]

Add #asGreaseByteArray as compatibility method for Collection and Integer #asByteArray methods. #asByteArray does not exist on integer classes in Squeak and GemStone.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (05a6c4e) 84.57% compared to head (f7d9822) 84.83%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #161      +/-   ##
==========================================
+ Coverage   84.57%   84.83%   +0.25%     
==========================================
  Files        2017     2045      +28     
  Lines       13558    13790     +232     
==========================================
+ Hits        11467    11699     +232     
  Misses       2091     2091              

Files	Coverage Δ
...Collection.extension/instance/greaseAsByteArray.st	100.00% <100.00%> (ø)
...e/GRPlatform.class/instance/integerAsByteArray..st	100.00% <100.00%> (ø)
...ge/Integer.extension/instance/greaseAsByteArray.st	100.00% <100.00%> (ø)
...e/LargeInteger.extension/instance/greaseByteAt..st	100.00% <100.00%> (ø)
...argeInteger.extension/instance/greaseBytesCount.st	100.00% <100.00%> (ø)
...e/SmallInteger.extension/instance/greaseByteAt..st	100.00% <100.00%> (ø)
...mallInteger.extension/instance/greaseBytesCount.st	100.00% <100.00%> (ø)
...e/LargeInteger.extension/instance/greaseByteAt..st	100.00% <100.00%> (ø)
...argeInteger.extension/instance/greaseBytesCount.st	100.00% <100.00%> (ø)
...e/SmallInteger.extension/instance/greaseByteAt..st	100.00% <100.00%> (ø)
... and 20 more

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[theseion]

@jbrichau I don't have GemStone. Could you add the necessary things for GemStone to this PR?

[jbrichau]

It turns out GLASS does include Integer>>asByteArray (https://github.com/glassdb/glass/blob/master/repository/Squeak.v36.package/Integer.extension/instance/asByteArray.st)

@theseion I added the missing methods for GemStone.

[jbrichau]

Looks good to me. Thanks!