Fix bug with extended DateTime, improve performance

[Tigrov]

• Fix bug with extended DateTime
• Improve performance of Json::encode() by 10-20%

About jsonSerialize()

The PHP documentation mentions: Returns data which can be serialized by json_encode()

The processObject() should return the result of jsonSerialize() without processing:

return $data->jsonSerialize();

But this breaks BC.

If it is requered to pre-process data for jsonSerialize(), this should be done inside jsonSerialize():

...
public function jsonSerialize(): mixed
{
    return Json:process($this->data);
}
...

What do you think? Do this for the next major version?

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌
Fixed issues	-

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (4b62dd2) 100.00% compared to head (d666c50) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #41 +/- ## =========================================== Coverage 100.00% 100.00% - Complexity 15 20 +5 =========================================== Files 1 1 Lines 31 37 +6 =========================================== + Hits 31 37 +6 ``` | [Files Changed](https://app.codecov.io/gh/yiisoft/json/pull/41?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft) | Coverage Δ | | |---|---|---| | [src/Json.php](https://app.codecov.io/gh/yiisoft/json/pull/41?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL0pzb24ucGhw) | `100.00% <100.00%> (ø)` | |

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[what-the-diff[bot]]

PR Summary

• Enhancing JSON Handling The JSON processing in our code has been boosted by making use of specialized JSON functions. This should make JSON encoding and decoding faster and more reliable.
• Improved Development Environment We've added more signposts for our developers in form of code annotations. These will help them understand the expected types of data and lower the chance of errors when working with JSON handling.
• Added Date/Time Extended Functionality A new file for more complex date and time operations has been created in the testing area. This lays the groundwork for improving how we manage and work with date and time across the platform, enhancing our application's flexibility.
• Testing Improvements We're now testing how our JSON processor handles specific scenarios like encoding an empty item or a date/time object. This will help ensure our code handles these situations correctly and should lead to a more robust, failure-resistant application.