r/aws_ec2_transit_gateway: Refactor tagging logic to keyvaluetags package.
r/aws_ec2_transit_gateway: Refactor tagging logic to keyvaluetags package.

kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws