Update tests for Decimal successor/predecessor for 2.0.0

[dehall]

CQL 2.0.0 changed the behavior of successor of Decimal and predecessor of Decimal to be aware of the precision of the Decimal. Previously these operators always added/subtracted 0.00000001. This PR marks the existing tests with versionTo="1.5.3" and adds new tests with version="2.0" and the updated behavior.

Note: I looked for other instances of an operator's behavior changing across versions and didn't see anything obvious. The only other instance I see of versionTo is on "DateTimeComponentFromTimezoneOffset" where the operator name changed between 1.3 and 1.4 and so the test name changed.
I point that out to say, I think this PR could set a precedent for this sort of scenario so I encourage the maintainers to be nitpicky. 3 alternatives I considered:

1. Only keeping one test with the latest version, ie setting version="2.0" and updating the expected result
2. Two tests, but the tests should use the same name instead of different names
3. Two tests, but the test names should indicate the version, eg "PredecessorOf1D_v200" or something along those lines

[dehall]

I suppose there's also option 4, add versioning info to the output instead, and the tests could then look something like this:

<test name="PredecessorOf1D" version="1.0">
  <expression>predecessor of 1.0</expression>
  <output versionTo="1.5.3">0.99999999</output>
  <output version="2.0">0.9</output>
</test>

But that's not currently supported by the schema and so is a larger change with more downstream impact

[bryantaustin13]

LGTM

[cmoesel]

Approved (on behalf of MITRE's JS cql-execution team).

That said, I noticed that there are predecessor tests for quantities but there are no successor tests for quantities. I'd accept this PR as-is because it is an improvement, but it would be a bonus if you could add successor tests for quantities as well.