Add Amazon S3 Cloud Sync KMS option for additional argument to rclone

Problem/Justification
At the moment rclone cloud sync fails when transferring to a Amazon S3 bucket which is secured with KMS. This is a feature request to add a tick box option to the Cloud Sync Tasks for Amazon S3 which just adds the additional parameter “–s3-server-side-encryption aws:kms” to the rclone arguments which is all that is needed to get it working. A general custom parameter for rclone feature request has been rejected on the basis you asked for individual parameter options - here is one.

Impact
Allows Amazon S3 Cloud Sync to work with a Bucket encrypted with KMS, which is a requirement for lots of enterprise customers.

User Story
I modified our cloud_sync.py to add this parameter in the section at line 160 and it works fine after restarting the TrueNAS or middlewared service.

Use a temporary file to store rclone file

async with RcloneConfig(cloud_sync) as config:
    args = [
        "rclone",
        "--config", config.config_path,
        "-v",
        "--s3-server-side-encryption", "aws:kms",
        "--stats", "1s",
    ]