add getDateTimeFormat() method to \Cycle\Database\Driver\Driver

[ddrv]

🔍 What was changed

A method for obtaining the time storage format has been added to the driver class. To avoid breaking backward compatibility, a separate interface has been allocated for this method.

🤔 Why?

In some cases, it is necessary to know in what format time is stored.
For example, see Issue 66 of cycle/migrations

📝 Checklist

• How was this tested:
  • Tested manually
  • Unit tests added

[roxblnfk]

Thank you for the PR and for digging into cycle/migrations#66!

After investigating, we fixed the issue entirely on the cycle/migrations side in cycle/migrations#67, without needing a new driver API: the migrator now passes created_at to the WHERE clause as a DateTimeInterface object instead of a pre-formatted string, so the driver formats it exactly the same way as on insert — consistently with the withDatetimeMicroseconds option. The migration table's datetime columns are also created with datetime(6) now, which fixes the related failure on SQL Server (legacy DATETIME rejects values with microseconds).

Since getDateTimeFormat() is no longer required for that fix, I'm closing this PR. If a use case comes up where exposing the driver's datetime format is genuinely needed, we can revisit the idea.