Convert `NaiveDate::from_num_days_from_ce` to return `Result`

[Zomtir]

This pull request targets the issue #1469. The implementation is based on the discussion in #1445.

• Convert NaiveDate::from_num_days_from_ce to return Result
• i32::checked_add() is mapped locally to an Err(Error::OutOfRange) for now

cc @pitdicker

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.34%. Comparing base (999582e) to head (bd44d85).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 0.5.x #1470 +/- ## ========================================== - Coverage 94.34% 94.34% -0.01% ========================================== Files 37 37 Lines 17009 17007 -2 ========================================== - Hits 16047 16045 -2 Misses 962 962 ```

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[pitdicker]

It may be for the best that you didn't start with the timestamp methods on NaiveDateTime #1471.

[pitdicker]

Your first one in :tada:.