Tweak some tests to provide coverage of new execution paths in the spec,
such as calling GetOptionsObject inside ToTemporal___; add a few new tests
for things that weren't covered before, such as rounding a PlainDateTime
at the edge of the range; and tweak the tests verifying when the
properties of the options bag are read, which I made a mistake in #4119.
See: https://github.com/tc39/proposal-temporal/pull/2925