[enhancement] move SMTP credentials to config

[winiar93]

Summary

Closes #4066

• SMTP credentials: Secret block now uses AWS credentials instead of Prefect secret block
• Email notifications: Enabled by providing smtp_credential_secret parameter (string with credential name) in the flow function and replaces the removed enable_notifications parameter
• Renamed variables:
  • recipients → notification_recipients
  • smtp_config → smtp_credential_secret
• Improved logging: Added more detailed logs throughout the flow

Importance

To centralize credentials management

Checklist

This PR:

• contains a summary of the changes (the "what")
• links the relevant issue with the Closes #<issue_number> phrase (the "why")
• adds new tests (if appropriate)
• updates docstrings for any new functions or function arguments (if appropriate)

[k-wolski]

LGTM! But it should be checked by Michał/Rafał as well before merge.

Please also bump viadot version, as it's necessary to release that fix.

[winiar93]

code was tested, works good after change

with adjusted logging which was requested