fix(gen2-migration): handle resource dependency patterns in custom resource migration

[sanjanaravikumar-az]

Fixes gaps in the custom resource transformer where Gen1 dependency patterns produced broken Gen2 output.

Changes:

• Track dependency variable names from addResourceDependency calls and transform their property access chains to Gen2 paths
• Transform cdk.Fn.ref() calls with property access arguments

Example:
cdk.Fn.ref(dependencies.api.app.GraphQLAPIIdOutput becomes backend.data.resources.cfnResources.cfnGraphqlApi.attrApiId

• Remove AmplifyDependentResourcesAttributes type-annotated variable declarations and strip type assertions
• Track and remove variable declarations calling functions imported from amplify-dependent-resources-ref
• Pass a single backend: any parameter to the generated constructor instead of individual category parameters

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