Fixes IR printing DV option set (#2116)

add AsDouble() (#1906)

Add helpers to say:

`double x = value.AsDouble();`  

or AsDecimal. 

this avoids having to cast and guess whether it's decimal or double.

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Co-authored-by: Mike Stall <jmstall@microsoft.com>

Allow Void expressions to be used within ForAll (#1527)

If a ForAll expression is used within a context where its result is not needed, then it should be able to use void expressions, like in the example below. This change allows it, making the entire result of the ForAll expression a void result.

    ForAll(
        Sequence(4),
        If(
            Mod(Value, 2) = 1,
Patch( table, Index(table, Value), { IsOdd: true } ), // this returns a
record, incompatible with tables
Collect( table, { Value: Value, IsOdd: false }, { Value: Value + 1,
IsOdd: true } // this returns a table
        )
    )

Fix #378 (#379)

* Fix #378
If(true, OptionSet.Option1)

OptionSetValue should derive from ValidFormulaValue, not FormulaValue

* Pr feedback

Co-authored-by: Mike Stall <jmstall@microsoft.com>