fix: limit SAR application test to regions that have SAR enabled, plus simplification for docker asset test (#2096)

Fixes test runs that try to deploy a SAR resource to regions that don't
support them. Supported regions are documented here:
https://docs.aws.amazon.com/general/latest/gr/serverlessrepo.html.

It also removes logic from
`packages/@aws-cdk-testing/cli-integ/tests/cli-integ-tests/deploy/cdk-deploy-docker-asset-multi-region.integtest.ts`
that depends on `process.env.AWS_REGIONS`, which isn't set in
Atmosphere-enabled runs.

This precedes an API change in an internal repo.

### Checklist
- [ ] This change contains a major version upgrade for a dependency and
I confirm all breaking changes are addressed
  - Release notes for the new version:

---
By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license

Author: iankhou

packages/@aws-cdk-testing/cli-integ/lib/regions.ts

@@ -43,11 +43,33 @@ export function allBut(exclude: string[]): string[] {
 }
 
 /**
- * Regions that don't support CloudFormation Stack Refactoring
+ * Regions that support CloudFormation Stack Refactoring
  */
 export const STACK_REFACTORING_REGIONS = allBut([
+  // Unsupported regions
   'ap-southeast-5',
   'ap-southeast-7',
   'mx-central-1',
 ]);
 
+/**
+ * Regions that support the Serverless Application Repository
+ *
+ * @see https://docs.aws.amazon.com/general/latest/gr/serverlessrepo.html
+ */
+export const SAR_REGIONS = allBut([
+  // Unsupported regions
+  'ap-northeast-3',
+  'af-south-1',
+  'ap-south-2',
+  'ap-southeast-3',
+  'ap-southeast-4',
+  'ap-southeast-5',
+  'ap-southeast-7',
+  'eu-central-2',
+  'eu-south-1',
+  'eu-south-2',
+  'il-central-1',
+  'ca-west-1',
+  'mx-central-1',
+]);

packages/@aws-cdk-testing/cli-integ/tests/cli-integ-tests/deploy/cdk-deploy-docker-asset-multi-region.integtest.ts

@@ -4,8 +4,7 @@ integTest(
   'deploy same docker asset to multiple regions',
   withDefaultFixture(async (fixture) => {
     const primaryRegion = fixture.aws.region;
-    const availableRegions = (process.env.AWS_REGIONS ?? 'us-east-1,us-west-2').split(',');
-    const secondaryRegion = availableRegions.find((r) => r !== primaryRegion) ?? 'us-west-2';
+    const secondaryRegion = ['us-east-1', 'us-west-2'].find((r) => r !== primaryRegion)!;
 
     // Bootstrap the secondary region (with the same random qualifier the app
     // is synthesized with, and a unique stack name to avoid clashing with

packages/@aws-cdk-testing/cli-integ/tests/cli-integ-tests/diff/cdk-diff---method-change-set-does-not-show-templateurl-change-for-sar-application.integtest.ts

@@ -1,4 +1,5 @@
 import { integTest, withSpecificFixture } from '../../../lib';
+import { SAR_REGIONS } from '../../../lib/regions';
 
 /**
  * Regression test for https://github.com/aws/aws-cdk-cli/issues/2025
@@ -21,5 +22,5 @@ integTest(
     // THEN
     expect(diff).not.toContain('TemplateURL');
     expect(diff).toContain('There were no differences');
-  }),
+  }, { aws: { regions: SAR_REGIONS } }),
 );