Mark results of type Decimal without decimal places explicitly as type=decimal

[dehall]

For detailed context on this PR, see Zulip thread here: #cql > Ambiguous Decimal/Integer Literals in Spec and Tests

In short, tests whose expected result is a Decimal without any decimal places are currently represented ambiguously. In some tests, the result is numeric without any decimal places, but technically that represents an Integer literal, not a Decimal. Alternatively, some tests use a Decimal literal, but doing so adds decimal places and implies a precision which should not be present in the final value.

This PR attempts to standardize by using the type parameter on the output, only on tests where the expected result is a Decimal with no decimal places.

Specifically:

• Power as of 2.0.0 always returns a Decimal, regardless of input https://cql.hl7.org/09-b-cqlreference.html#power
• TruncatedDivide returns a Decimal if at least one operand is a Decimal (other numeric values get promoted to Decimal) https://cql.hl7.org/09-b-cqlreference.html#truncated-divide
• Round, with precision 0 or unspecified, returns a Decimal with no decimal places https://cql.hl7.org/09-b-cqlreference.html#round

[dehall]

Discussed at connectathon breakout session: the tests where the expected type changed between 1.5.3 and 2.0.0 need to be versioned, so I'll update those