[FEAT] Implement Refund for JPMorgan

this connector lacks basic feature i.e., refunds.

relevant docs:

- https://developer.payments.jpmorgan.com/api/commerce/online-payments/overview
- https://developer.payments.jpmorgan.com/api/commerce/online-payments/online-payments/online-payments#/operations/V2RefundPost
<think>
PR Context:
- Title: feat(connector): [jpmorgan] implement refund flow
- Merged: 2025-06-25T07:01:17Z
- Files changed: 3 files
- Commits: 4 commits

Implementation approach:
## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [x] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [x] CI/CD

## Description
<!-- Describe your changes in detail -->

This PR implements refund flow for JPMorgan connector. Connector returns `Authorized` state (`Pending`). Post RSync call, the status gets updated to `Success`.

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This 
</think>

To implement this, you'll need to modify:


**Detailed Implementation:**


**Commit 1:** feat(connector): [jpmorgan] implement refund flow (#8436)
Files to modify:


**crates/hyperswitch_connectors/src/connectors/jpmorgan.rs**
  Modify existing code

**crates/hyperswitch_connectors/src/connectors/jpmorgan/transformers.rs**
  Remove:
    - struct: pub::MerchantSoftware
    - struct: pub::RefundResponse
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