(feat) Date set time from another date.

**Feature Description**
It would be great if there is a method to set the time from another date.

```ts
dayjs('2021-03-01T12:34:56.123Z').setTimeFrom(
dayjs('2021-02-28T10:05:12.870Z')
);

// Result: '2021-03-01T10:05:12.870Z'
```

I know there are alternatives and I could write my own method. This is just a suggestion.
Use case: Merge two dates which comes from separat inputs date and time.

day.js `1.10.4`

No file, test, or entry point is named. Start by locating Day.js's existing date-manipulation APIs and related tests, then compare their behavior with the example in the issue. Done means a date can take the time components from another date while preserving its own date components, with tests covering the shown result.

Written by the indexing model from the issue text.