Fix inconsistency in S3 transfer operators

[yuseok89]

Changes

Change	FTPToS3	SFTPToS3	S3ToFTP	S3ToSFTP
Rename s3_conn_id → aws_conn_id (deprecated alias kept)	—	✅	—	—
S3 upload options (replace, encrypt, gzip, acl_policy)	—	✅	—	—
Multi-file support (*_filenames params)	—	✅	✅	✅
fail_on_file_not_exist	✅	—	✅	✅

✅ added in this PR — already existed

Upcoming

Integration tests covering multi-file transfer and fail_on_file_not_exist against real SFTP/FTP servers will be added in a follow-up commit.

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