Provide a way to access secondary index name in lambda function

### Environment information

```plain text
System:
OS: macOS 15.0
CPU: (8) arm64 Apple M3
Memory: 114.58 MB / 24.00 GB
Shell: /bin/zsh
Binaries:
Node: 22.8.0 - ~/.nvm/versions/node/v22.8.0/bin/node
Yarn: undefined - undefined
npm: 10.8.2 - ~/.nvm/versions/node/v22.8.0/bin/npm
pnpm: 9.11.0 - ~/.nvm/versions/node/v22.8.0/bin/pnpm
NPM Packages:
@aws-amplify/auth-construct: 1.3.1
@aws-amplify/backend: 1.3.0
@aws-amplify/backend-auth: 1.2.0
@aws-amplify/backend-cli: 1.2.8
@aws-amplify/backend-data: 1.1.4
@aws-amplify/backend-deployer: 1.1.4
@aws-amplify/backend-function: 1.5.0
@aws-amplify/backend-output-schemas: 1.2.0
@aws-amplify/backend-output-storage: 1.1.2
@aws-amplify/backend-secret: 1.1.3
@aws-amplify/backend-storage: 1.2.0
@aws-amplify/cli-core: 1.1.3
@aws-amplify/client-config: 1.3.2
@aws-amplify/deployed-backend-client: 1.4.1
@aws-amplify/form-generator: 1.0.3
@aws-amplify/model-generator: 1.0.8
@aws-amplify/platform-core: 1.1.0
@aws-amplify/plugin-types: 1.3.0
@aws-amplify/sandbox: 1.2.2
@aws-amplify/schema-generator: 1.2.4
aws-amplify: 6.6.3
aws-cdk: 2.160.0
aws-cdk-lib: 2.158.0
typescript: 5.6.2
AWS environment variables:
AWS_STS_REGIONAL_ENDPOINTS = regional
AWS_NODEJS_CONNECTION_REUSE_ENABLED = 1
AWS_SDK_LOAD_CONFIG = 1
No CDK environment variables
npm notice
npm notice New patch version of npm available! 10.8.2 -> 10.8.3
npm notice Changelog: https://github.com/npm/cli/releases/tag/v10.8.3
npm notice To update run: npm install -g npm@10.8.3
npm notice
```

### Describe the feature

Get the secondary index name programmatically.

### Use case

To query dynamodb items in lambda function.

This is my model definition:

```typescript
import { a } from "@aws-amplify/backend";

export default a
.model({
id: a.id().required(),
key: a.ref("ConfigurationKey").required(),
booleanValue: a.boolean(),
stringValue: a.string(),
})
.secondaryIndexes((index) => [index("key")]);

```

Secondary index generated in dynamodb:

Start from the TypeScript model definition and the generated DynamoDB secondary index described in the issue. Trace how the model and its index metadata become available to the Lambda function, then identify the existing tests or entry points for generated model configuration. Done means a Lambda can obtain the secondary index name programmatically and use it to query DynamoDB.

Written by the indexing model from the issue text.