Revert "JsonNodeEquivalence: fix numeric value hashcode (hopefully) :("

This reverts commit 811619ed4cd7256ce545c1b4f1762e8fc18211e3.

It was the wrong way to go entirely.
JsonNodeEquivalence: more solid implementation of numeric node hashcodes

We grab the decimal and try and convert it into a BigInteger, if we succeed we
take the hashcode of that. Otherwise, strip the zeroes off the decimal and use
this hashcode.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
JsonNodeEquivalenceTest: add more tests for various decimal values

All work. Looks good. At last.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>