Replace const.txt file input with synthetic inputs

This commit replaces file resource-based test inputs with in-memory
equivalents.  This is more consistent and efficient than the previous
approach.  Also resized some test inputs to be partSize + 1 instead of
2 * partSize.  Tested against aws-s3, blobstore, core, cloudfiles-us,
and filesystem.
> I prefer the most restrictive access modifier

I understand, but if we feel it may make sense for you to override `XML` and `XML2` in subclasses, wouldn't you expect the same to be true for `oneHundredOneConstitutions`? Also, any reason for not using UPPER_UNDERSCORE here?

Either way, these are all minors - no need to change. Thanks for the cleanup!