helper/resource: Ensure -sweep-run filtering includes sweeper dependencies

[bflad]

Previously, the -sweep-run filtering would only add sweepers matching the filter, but miss the dependencies. In real world usage:

	resource.AddTestSweepers("aws_vpc", &resource.Sweeper{
		Name: "aws_vpc",
		Dependencies: []string{
			"aws_egress_only_internet_gateway",
			"aws_internet_gateway",
			"aws_nat_gateway",
			"aws_network_acl",
			"aws_route_table",
			"aws_security_group",
			"aws_subnet",
			"aws_vpc_peering_connection",
			"aws_vpn_gateway",
		},
		F: testSweepVPCs,
	})

Where resources like aws_subnet would contain further dependencies that would cause failures if not removed, e.g.

$ go test ./aws -v -timeout=10h -sweep=us-west-2 -sweep-run=aws_vpc -sweep-allow-failures
...
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_egress_only_internet_gateway), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_internet_gateway), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_nat_gateway), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_network_acl), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_route_table), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_security_group), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_subnet), but that sweeper was not found
2019/10/27 16:10:29 [DEBUG] Sweeper (aws_vpc) has dependency (aws_vpc_peering_connection), running..
...
2019/10/27 16:11:32 Sweeper Tests ran successfully:
	- aws_vpc_dhcp_options
	- aws_vpc_peering_connection
	- aws_vpc_endpoint
	- aws_vpc_endpoint_service
2019/10/27 16:11:32 Sweeper Tests ran unsuccessfully:
	- aws_vpc: Error deleting VPC (vpc-0f3da92fc03d683b7): DependencyViolation: The vpc 'vpc-0f3da92fc03d683b7' has dependencies and cannot be deleted.

After changes:

$ go test ./aws -v -timeout=10h -sweep=us-west-2 -sweep-run=aws_vpc -sweep-allow-failures
...
2019/10/27 18:44:58 Sweeper Tests ran successfully:
	- aws_autoscaling_group
	- aws_db_subnet_group
	- aws_vpc_endpoint_service
	- aws_route_table
	- aws_batch_job_queue
	- aws_beanstalk_environment
	- aws_cloudhsm_v2_cluster
	- aws_fsx_windows_file_system
	- aws_ec2_client_vpn_endpoint
	- aws_elasticache_replication_group
	- aws_sagemaker_notebook_instance
	- aws_vpc_dhcp_options
	- aws_vpc_endpoint
	- aws_mq_broker
	- aws_msk_cluster
	- aws_network_interface
	- aws_batch_compute_environment
	- aws_elasticache_cluster
	- aws_lambda_function
	- aws_instance
	- aws_vpn_gateway
	- aws_nat_gateway
	- aws_vpc_peering_connection
	- aws_directory_service_directory
	- aws_ec2_transit_gateway_vpc_attachment
	- aws_elb
	- aws_emr_cluster
	- aws_fsx_lustre_file_system
	- aws_security_group
	- aws_egress_only_internet_gateway
	- aws_db_instance
	- aws_lb
	- aws_redshift_cluster
	- aws_internet_gateway
	- aws_dx_gateway_association_proposal
	- aws_eks_cluster
	- aws_network_acl
	- aws_elasticsearch_domain
	- aws_api_gateway_vpc_link
	- aws_route53_resolver_endpoint
	- aws_spot_fleet_request
	- aws_dx_gateway_association
2019/10/27 18:44:58 Sweeper Tests ran unsuccessfully:
	- aws_vpc: Error deleting VPC (vpc-0f3da92fc03d683b7): DependencyViolation: The vpc 'vpc-0f3da92fc03d683b7' has dependencies and cannot be deleted.
	status code: 400, request id: 00c178dd-1a3c-45fc-9802-e8215322a54b
	- aws_subnet: Error deleting Subnet (subnet-075212958430d977f): DependencyViolation: The subnet 'subnet-075212958430d977f' has dependencies and cannot be deleted.
	status code: 400, request id: ded1a6e7-c13f-45df-82e3-a53c27f9c8e6

It's worth noting that the sweeper framework would likely benefit from creating a proper directed acyclic graph, but that is certainly outside the scope of this fix.

[radeksimko]

Thank you for the bug fix and very thorough testing! 👍

[appilon]

I'm going to merge this since it was approved okay @radeksimko and @bflad

[ghost]

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