r/aws_amplify_app: Add test sweeper.

Acceptance test output:

% TEST=./aws SWEEP=us-west-2 SWEEPARGS=-sweep-run=aws_amplify_app make sweep
WARNING: This will destroy infrastructure. Use only in development accounts.
go test ./aws -v -sweep=us-west-2 -sweep-run=aws_amplify_app -timeout 60m
2021/05/20 11:13:49 [DEBUG] Running Sweepers for region (us-west-2):
2021/05/20 11:13:49 [DEBUG] Running Sweeper (aws_amplify_app) in region (us-west-2)
2021/05/20 11:13:49 [INFO] AWS Auth provider used: "EnvProvider"
2021/05/20 11:13:49 [DEBUG] Trying to get account information via sts:GetCallerIdentity
2021/05/20 11:13:50 [DEBUG] Trying to get account information via sts:GetCallerIdentity
2021/05/20 11:13:50 [DEBUG] Deleting Amplify App (d3e2rpqo82owxg)
2021/05/20 11:13:51 Sweeper Tests ran successfully:
	- aws_amplify_app
ok  	github.com/terraform-providers/terraform-provider-aws/aws	4.452s

aws/internal/service/amplify/lister/list.go

@@ -0,0 +1,3 @@
+//go:generate go run ../../../generators/listpages/main.go -function=ListApps github.com/aws/aws-sdk-go/service/amplify
+
+package lister

aws/resource_aws_amplify_app_test.go

@@ -3,20 +3,70 @@ package aws
 import (
 	"encoding/base64"
 	"fmt"
+	"log"
 	"os"
 	"regexp"
 	"testing"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/amplify"
+	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/acctest"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/amplify/finder"
+	"github.com/terraform-providers/terraform-provider-aws/aws/internal/service/amplify/lister"
 	"github.com/terraform-providers/terraform-provider-aws/aws/internal/tfresource"
 )
 
-// TODO sweeper
+func init() {
+	resource.AddTestSweepers("aws_amplify_app", &resource.Sweeper{
+		Name: "aws_amplify_app",
+		F:    testSweepAmplifyApps,
+	})
+}
+
+func testSweepAmplifyApps(region string) error {
+	client, err := sharedClientForRegion(region)
+	if err != nil {
+		return fmt.Errorf("error getting client: %s", err)
+	}
+	conn := client.(*AWSClient).amplifyconn
+	input := &amplify.ListAppsInput{}
+	var sweeperErrs *multierror.Error
+
+	err = lister.ListAppsPages(conn, input, func(page *amplify.ListAppsOutput, lastPage bool) bool {
+		if page == nil {
+			return !lastPage
+		}
+
+		for _, app := range page.Apps {
+			r := resourceAwsAmplifyApp()
+			d := r.Data(nil)
+			d.SetId(aws.StringValue(app.AppId))
+			err = r.Delete(d, client)
+
+			if err != nil {
+				log.Printf("[ERROR] %s", err)
+				sweeperErrs = multierror.Append(sweeperErrs, err)
+				continue
+			}
+		}
+
+		return !lastPage
+	})
+
+	if testSweepSkipSweepError(err) {
+		log.Printf("[WARN] Skipping Amplify Apps sweep for %s: %s", region, err)
+		return sweeperErrs.ErrorOrNil() // In case we have completed some pages, but had errors
+	}
+
+	if err != nil {
+		sweeperErrs = multierror.Append(sweeperErrs, fmt.Errorf("error listing Amplify Apps: %w", err))
+	}
+
+	return sweeperErrs.ErrorOrNil()
+}
 
 func TestAccAWSAmplifyApp_basic(t *testing.T) {
 	var app amplify.App