[Gen 2] Support cross-region functions

[ykethan]

Describe the feature you'd like to request

similar to gen 1: https://docs.amplify.aws/gen1/react/build-a-backend/graphqlapi/custom-business-logic/#calling-functions-in-different-regions
reference a existing function in gen 2 can be done using a.handler.function('<function-name>')
but cross region isnt supported

Describe the solution you'd like

a.handler.function('<function-name>', '<region>')

Describe alternatives you've considered

override backend.ts to addLambdaDataSource

Additional context

No response

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this feature request

Would this feature include a breaking change?

• ⚠️ This feature might incur a breaking change

[JGamboa]

Basically the idea is to have some of the functions on another regions because of latency.

On my case we have to connect to apis on different countries, this countries have low bandwitch to US, so creating the function on for example SA give us better performance, even when the appsync is on the US.

APP SYNC US -> LAMBDA US ->>> SA COUNTRY -->> LOW RESPONSE
APP SYNC US -> LAMBDA SA ->>> SA COUTRY ---> FAST RESPONSE