Correct longAsInt output in the stress test application

Correct longAsInt output in the stress test application

RNG-171 changed the cached int source to output a long as two ints using
the low 32-bits, then high 32-bits.

Updated the RngDataOutput to support HiLo or LoHi. Added tests for each
implementation.

Dropped high-bits and low-bits command options. Added source64 option
with enum for high, low, high-Low, low-high, long, int. The default for
stress testing matches the caching implementation.

Update the test documentation to reflect the changes.