Add S3TablesCreateNamespaceOperator

[john-jac]

What

Add S3TablesCreateNamespaceOperator to create namespaces in Amazon S3 Tables table buckets.

Why

Namespaces organize tables within a table bucket (table bucket → namespace → table). The existing system test used a @task with raw boto3 — this operator replaces that workaround and completes the S3 Tables resource hierarchy.

What was done

• Operator: S3TablesCreateNamespaceOperator with if_exists idempotency, added to existing s3_tables.py
• Unit tests: Added to existing test_s3_tables.py — happy path, skip-existing, fail-on-conflict, template fields
• System test: Updated example_s3_tables.py — replaced @task create_namespace with operator
• Docs: Updated s3_tables.rst with new section

[vincbeck]

Please check which files are being committed before creating the PR

[github-actions]

Backport failed to create: v3-2-test. View the failure log Run details

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
❌	v3-2-test

You can attempt to backport this manually by running:

cherry_picker 966b0ec v3-2-test

This should apply the commit to the v3-2-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

If you don't have cherry-picker installed, see the installation guide.