[WIP] Migrate core EmailOperator to SMTP provider

[hussein-awala]

closes: #30530

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In this PR, we migrate core EmailOperator to SMTP provider, and we deprecate the core one.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[ITJamie]

This warning assumes incorrectly that it has to fallback to cfg settings to find a username or password for smtp. Not all smtp servers require authentication to send mail.

It can not be assumed that if a connection has no username or password that the connection config is wrong and thus falling back to legacy config

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[eladkal]

@hussein-awala i think now that main branch is Airflow 3 this PR should be easier

[eladkal]

@hussein-awala will you have time to complete this one?

[hussein-awala]

@hussein-awala will you have time to complete this one?

I will try to complete it by tomorrow.

[hussein-awala]

@eladkal I think there is no need to migrate it, we can delete the resources we want to deprecate and clean the code. I created this draft: #46041.

For version 2.11, and since the provider operator and SMTP Notifer have been introduced for quite some time, we don't need to create a complicated backport, IMHO it will be enough to inform/warn users about the upcoming deprecation. WDYT?

[eladkal]

I agree. The goal is to remove email integration from core completely

[eladkal]

Do we need to keep it?
We migrated almost all core operators to standard provider.
Should we just remove this file?