fix : perf issue with Class.forName with Kotlinx Datetime

[fhebuterne]

Hi,

Since kmongo 4.7.2, performance has been degraded by Class.forName with kotlinx datetime during our requests to DB.

We not using kotlinx datetime lib, so Class.forName is call each time.

By using AsyncProfiler on wall mode, we can see it :

For an hotfix for us, we added kotlinx datetime to fix issue in our side, waiting a fix on KMongo.

I have added a fix on this PR, by loading Class.forName only on first time.

Could you check it, please 🙏 ?

Sincerely,
Fabien

[zigzago]

Thank you for the PR.