Add support & test cases for MSSQL Source via SSH tunnels

[alexandr-shegeda]

Tell us about the problem you're trying to solve

We'd like to add support for SSH tunnels for the existing MSSQL source. This will allow connecting to the source from the different VPC.

Describe the solution you’d like

There are few main steps to accomplish this requirement:

1. Create a DB in AWS through terraform or the UI. We already have a blueprint for how to create a database on AWS in terraform. You would need only to create a database without a public IP in the subnet which already exists, the same one the Postgres DB is currently linked to. Please talk to Oleksandra for getting access to the AWS dev environment where you can spin up a database. If you go this route, you can re-use many of the parameters (tunnel host, tunnel key, etc..) in the lastpass secrets Postgres Source ssh key creds and destination postgres test creds with sshkey. If Terraform is slowing you down too much feel free to create one in the UI.
2. Wrap existing MSSQL source with SshWrappedSource and check that additional SSH configuration properties are present on UI
3. Cover this change with an appropriate number of unit/integration/acceptance tests

Describe the alternative you’ve considered or used

Depending on whether you are adding a source or a destination the impl is slightly different. See the instructions for how to add SSH support to a connector

Example PR of adding SSH support to the Postgres source

Note that this PR has way more logic in them than what you'll need to implement for a single connector because they add common helpers and shared libraries and docs