Support SSH connection via bastion host

[bpg]

Is your feature request related to a problem? Please describe. Allow the provider to establish connection to a PVE node via SSH bastion host.

Related discussions / questions:

• https://github.com/bpg/terraform-provider-proxmox/issues/701#issuecomment-1846957121
• https://github.com/bpg/terraform-provider-proxmox/issues/812#issuecomment-1867732335

Describe the solution you'd like Add bastion_host argument to provider's ssh config block, that specifies a bastion host that the provider should be using for establishing an SSH connection to PVE node(s). The provider can only be using SSH agent to connect to the bastion, as well as to the nodes behind.

Describe alternatives you've considered N/A

Additional context N/A

[bitchecker]

Hi @bpg, related to this enhancement, if someone uses a bastion host with high probability direct access to web can be disabled, so both (web+ssh) connections should be proxied via ssh.

[bpg-autobot[bot]]

Marking this issue as stale due to inactivity in the past 180 days. This helps us focus on the active issues. If this issue is reproducible with the latest version of the provider, please comment. If this issue receives no comments in the next 30 days it will automatically be closed. If this issue was automatically closed and you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thank you!