Snowflake destination: support key/passphrase auth

[marcosmarxm]

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┆Issue is synchronized with this Asana task by Unito

[sashaNeshcheret]

We have a close issue, that will add non encrypted private/public keys auth to Snowflake, so in scope of this ticket we should add ability for encrypting key and it will applicable only for destination.
@grishick should we create the same one for source?