[BUG] API Document generation does not parse request parameters for RPC types (Dubbo/SOFA/TARS/gRPC)

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Current Behavior

The API document generation in `ApiDocRegistrarImpl.getDocument()` uses `OpenApiUtils.generateDocumentParameters()` for all RPC types without distinction. This method only supports parsing Spring Web annotations (`@RequestParam`, `@RequestPart`, path variables) for HTTP-style parameters. For non-HTTP RPC types (Dubbo, SOFA, TARS, gRPC), it fails to extract any meaningful request parameter information, since these RPC types do not use Spring Web annotations.

As a result, the generated API document for RPC types contains `responseType` (response details) but has empty/missing request parameter details — the document only has response, no request.

### Expected Behavior

_No response_

### Steps To Reproduce

_No response_

### Environment

```markdown
ShenYu version(s):
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### Debug logs

_No response_

### Anything else?

_No response_

Start at ApiDocRegistrarImpl.getDocument() and trace how OpenApiUtils.generateDocumentParameters() is applied to each RPC type. Compare the request-parameter handling for Dubbo, SOFA, TARS, and gRPC, then verify that generated API documents include request details as well as the existing responseType information.

Written by the indexing model from the issue text.