(hotswap): Support for Hotswapping AppSync Pipeline Resolvers

### Describe the feature

Today, AppSync Unit resolvers support hotswap, but Pipeline resolvers explicitly do not https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk/lib/api/hotswap/appsync-mapping-templates.ts#L16-L24

I'd like to understand a bit more about the limitations here, if we're not changing the functions within a pipeline, and just update the templates or code are we able to resolve the existing function ids when performing the swap (we're able to resolve the apiId today, so I'd think this is basically equivalent).

### Use Case

I'd love to have a more fluid iteration experience while working on the business logic for my AppSync APIs.

I've written up a series of feature requests which I think will add to a faster, more fluid experience for AppSync users:
* https://github.com/aws/aws-cdk/issues/24111
* https://github.com/aws/aws-cdk-cli/issues/872
* https://github.com/aws/aws-cdk-cli/issues/871

### Proposed Solution

Support hotswapping templates and code in pipeline appsync resolvers.

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### CDK version used

2.64.0

### Environment details (OS name and version, etc.)

osx 13.2

Start by reading packages/aws-cdk/lib/api/hotswap/appsync-mapping-templates.ts, especially the existing exclusion for Pipeline resolvers, and trace how AppSync unit-resolver hotswaps resolve the API and function identifiers. Confirm the limitations for unchanged pipeline functions, then verify that pipeline resolver templates and code can be hotswapped without changing function IDs.

Written by the indexing model from the issue text.