LibJS/Temporal: Fix rounding in DifferenceInstant

[snooze6214]

Ticks two boxes in #15525

• Normative: Fix rounding in DifferenceInstant
• Editorial: Rename balanceResult to result on step 5.2 of DifferenceTemporalZonedDateTime

[snooze6214]

@linusg I made all the requested changes. Also 2 of the test-js tests seem to fail now because of the new rounding, what should I do about them? Thanks for reviewing ^^

[linusg]

Investigate if the new results are correct according to the changed spec, and update the test if so. Otherwise, check if your implementation has a bug and file a spec issue if everything is implemented according to spec but still yields wrong results.

[snooze6214]

@linusg alright! Done :)

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions!

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions!

[stale[bot]]

This pull request has been closed because it has not had recent activity. Feel free to re-open if you wish to still contribute these changes. Thank you for your contributions!