Change MergeLargestUnitOption to match spec
Change MergeLargestUnitOption to match spec

This was previously done with the spread syntax, but we are going to make
a change to it, so we'll need a function instead. The spec text has the
operation MergeLargestUnitOption, so name it that.

The ObjectCreate(null) step was previously missing, so add it in order to
be compliant with the spec.

UPSTREAM_COMMIT=1660e23ae982d84ff7958c85fb44ae981e315d59

js-temporal/temporal-polyfill,js-temporal/temporal-polyfill,js-temporal/temporal-polyfill