fix(cli): bootstrap respects qualifier from cdk.json (#31410)

closes #28249. 

The qualifier property can be set via the context key "@aws-cdk/core:bootstrapQualifier" and if omitted, the arbitrary default is `hnb659fds`. In the case of `cdk bootstrap`, there is an additional way to set the qualifier via the `--qualifier` CLI option. Specific to the `cdk bootstrap` logic, we currently only honor the command line argument, which is an error.

Ultimately, the following `cdk bootstrap` calls should be identical:

- `cdk bootstrap` with the following `cdk.json` file:

```json
{
  "@aws-cdk/core:bootstrapQualifier": "abcde",
}
```

- `cdk bootstrap --qualifier="abcde"`

I've made the decision that the `--qualifier` parameter takes precedent over the `cdk.json` context if they are both set.

packages/aws-cdk/lib/api/bootstrap/bootstrap-props.ts

@@ -129,5 +129,4 @@ export interface BootstrappingParameters {
    * @default - No value, optional argument
    */
   readonly customPermissionsBoundary?: string;
-
 }

packages/aws-cdk/lib/cli.ts

@@ -547,7 +547,7 @@ export async function exec(args: string[], synthesizer?: Synthesizer): Promise<n
             bucketName: configuration.settings.get(['toolkitBucket', 'bucketName']),
             kmsKeyId: configuration.settings.get(['toolkitBucket', 'kmsKeyId']),
             createCustomerMasterKey: args.bootstrapCustomerKey,
-            qualifier: args.qualifier,
+            qualifier: args.qualifier ?? configuration.context.get('@aws-cdk/core:bootstrapQualifier'),
             publicAccessBlockConfiguration: args.publicAccessBlockConfiguration,
             examplePermissionsBoundary: argv.examplePermissionsBoundary,
             customPermissionsBoundary: argv.customPermissionsBoundary,

packages/aws-cdk/test/cdk-toolkit.test.ts

@@ -69,6 +69,7 @@ import { HotswapMode } from '../lib/api/hotswap/common';
 import { Template } from '../lib/api/util/cloudformation';
 import { CdkToolkit, Tag } from '../lib/cdk-toolkit';
 import { RequireApproval } from '../lib/diff';
+import { Configuration } from '../lib/settings';
 import { flatten } from '../lib/util';
 
 let cloudExecutable: MockCloudExecutable;
@@ -115,7 +116,6 @@ describe('readCurrentTemplate', () => {
   let mockForEnvironment = jest.fn();
   let mockCloudExecutable: MockCloudExecutable;
   beforeEach(() => {
-
     template = {
       Resources: {
         Func: {
@@ -394,6 +394,29 @@ describe('readCurrentTemplate', () => {
   });
 });
 
+describe('bootstrap', () => {
+  test('accepts qualifier from context', async () => {
+    // GIVEN
+    const toolkit = defaultToolkitSetup();
+    const configuration = new Configuration();
+    configuration.context.set('@aws-cdk/core:bootstrapQualifier', 'abcde');
+
+    // WHEN
+    await toolkit.bootstrap(['aws://56789/south-pole'], bootstrapper, {
+      parameters: {
+        qualifier: configuration.context.get('@aws-cdk/core:bootstrapQualifier'),
+      },
+    });
+
+    // THEN
+    expect(bootstrapper.bootstrapEnvironment).toHaveBeenCalledWith(expect.anything(), expect.anything(), {
+      parameters: {
+        qualifier: 'abcde',
+      },
+    });
+  });
+});
+
 describe('deploy', () => {
   test('fails when no valid stack names are given', async () => {
     // GIVEN