Support for applying without -target

[tionichm]

what

This pull request introduces the ability to deploy a new VPC, subnets, and a peering connection without needing to use -target. It achieves this by adding variables for the manual specification of VPC CIDR blocks and route table IDs.

This should be backwards compatible with versions greater than 1.0.0 of this module.

• Added additional vars for VPC CIDR blocks.
• Added additional vars for route table IDs.
• Enhanced logic for creating routes.
• Added a new test that demonstrates creating a VPC, subnets, and a peering connection in one terraform apply.
• Added documentation for the single-apply approach.

why

• Closes examples/complete #50
• Closes The count fails in resource "aws_route" "requestor" #19