feat: add `var.ami_id` to fix the AMI used for the Bastion

[kayman-mk]

Description

The infrastructure should be immutable, i.e. applying the same infrastructure every week shouldn't change anything. At the moment the AMI id changes when a new AMI is published. This might introduce problems as the image is changed. It also increases the elapsed time of your workflows/pipelines by roughly 4 minutes.

This PR adds an optional var.ami_id. In case it is filled, this AMI is used for the Bastion EC2 instance. The var.ami_name_filter is now deprecated and will be removed with version 3.0.0 of the module.

I recommend using this new parameter. But make sure that you have an update procedure in place to update the AMI id regularly.

Verification

Apply the simple example --> Bastion host is setup and boots

Checklist

• [x] My code follows the style guidelines of the project
• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation

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