(appsync): add syncConfig to Resolver and AppsyncFunction

### Describe the feature

Add sync config property to Resolver and AppsyncFunction.
This property can be used in L1 Construct.

https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_appsync.CfnResolver.html#syncconfig
https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_appsync.CfnFunctionConfiguration.html#syncconfig

### Use Case

To set a Sync configuration for a resolver.

### Proposed Solution

Add missing property to the L2 constructs.

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.141.0

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

MacOS

Start at the L2 Resolver and AppsyncFunction entry points and compare their properties with the linked L1 CfnResolver.syncconfig and CfnFunctionConfiguration.syncconfig definitions. Add the missing sync configuration support to both constructs, then run the relevant AppSync construct tests and verify the synthesized output includes the configuration.

Written by the indexing model from the issue text.