Option to add tunnel1_ike_versions

[nikhilk145]

Currently, the Terraform module does not support specifying IKE versions for VPN tunnels. This causes limitations when we need to enforce specific IKE versions (for example, IKEv2) to comply with organization-wide security policies or customer VPN requirements.

Add support for tunnel1_ike_versions and tunnel2_ike_versions parameters in the module. These should allow users to define the permitted IKE versions for each VPN tunnel and pass them directly to the aws_vpn_connection resource.
Example:

tunnel1_ike_versions = ["ikev2"]
tunnel2_ike_versions = ["ikev2"]