Issue:
[FEATURE] Add Refund Sync route in Stripe compatibility

### Feature Description

There is a refund sync route https://github.com/juspay/hyperswitch/blob/573a4d384ee6a9d72648ab537804799a3993e1e8/crates/router/src/routes/app.rs#L184 

A similar route needs to be added in the compatibility layer in this file - https://github.com/juspay/hyperswitch/blob/main/crates/router/src/compatibility/stripe/refunds.rs 


### Possible Implementation


refer similar route of payments as an example. - https://github.com/juspay/hyperswitch/blob/573a4d384ee6a9d72648ab537804799a3993e1e8/crates/router/src/compatibility/stripe/app.rs#L12 

### Have you spent some time to check if this feature request has been raised before?

- [X] I checked and didn't find similar issue

### Have you read the Contributing Guidelines?

- [X] I have read the [Contributing Guidelines](https://github.com/juspay/hyperswitch/blob/main/docs/CONTRIBUTING.md)

### Are you willing to submit a PR?

None

Resolution:
<think>
PR Context:
- Title: feat(compatibility): add refund retrieve endpoint which accepts gateway creds
- Merged: 2023-04-24T19:52:10Z
- Files changed: 3 files
- Commits: 3 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [ ] New feature
- [x] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
This PR is based on the issue #920 to add refund sync with gateway creds in stripe compatibility.  
Adds a new service  refund_retrieve_with_gateway_creds which parses the JSON to type RefundsRetrieveRequest which already has an optional fiel
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** feat(compatibility): add refund retrieve endpoint which accepts gateway creds (#958)
Files to modify:


**crates/router/src/compatibility/stripe/app.rs**
  Modify existing code

**crates/router/src/compatibility/stripe/refunds.rs**
  Add:
    - function: pub::refund_retrieve_with_gateway_creds