Add tests for Format roundFactor

[ColinKerr]

We have tests confirming that the Format.roundFactor attribute is round tripped but no tests validating that it is properly handled in the C++ or TypeScript formatting code.

See documentation for roundFactor here: https://www.itwinjs.org/bis/ec/ec-format

Add tests in C++ and TypeScript

[hl662]

Adding information, based on my very short search, core-quantity has some tests set up for rounding, but none of the FormatSpecs used in the tests seem to pass in a roundFactor to it's properties.

[naronchen]

roundFactor is used in formatMagnitude which is referenced in

• formatQuantity link
  • also formatCompositePart link, called by formatComposite in formatQuantity
• formatRatio link

will add a couple tests there.

will do the same on cpp side