Fix JSON-RPC request error handling and pending request cleanup

[gioalex07]

Summary

This PR fixes a few issues in the JSON-RPC layer that could affect plugin stability, especially around internal
requests like refresh_credentials().

What Changed

• Return immediately after sending InvalidParams for requests with bad arguments
• Stop trying to respond to notifications with invalid params
• Clean up pending _requests_futures entries after handling a response
• Abort and clear pending internal requests when the connection closes
• Rebuild remote errors into their original specific types instead of always raising generic JsonRpcError
• Add regression tests for:
  • invalid request params
  • invalid notification params
  • pending request cleanup after success/failure
  • aborted refresh_credentials() on close
  • preservation of specific remote error types

Root Cause

There were three related problems in jsonrpc.py:

1. After detecting invalid params, the handler still continued execution and used bound_args even when binding had
   failed.
2. Outgoing request futures were never removed from _requests_futures, even after receiving a response or closing
   the connection.
3. Remote error responses were reconstructed as generic JsonRpcError, which discarded the original application-
   specific error type.

Impact

These issues could lead to:

• unexpected UnboundLocalError after InvalidParams
• hanging internal requests if the connection closed before a response arrived
• memory/state leaks in _requests_futures
• degraded error handling in plugins that rely on specific exceptions from refresh_credentials()

Validation

Validated with targeted local reproductions covering:

• invalid request params no longer crashing the handler
• invalid notifications no longer emitting bogus responses
• remote errors being raised as their specific original types
• pending request futures being cleared after response handling and on connection close

Notes

This PR is intentionally limited to the JSON-RPC layer and regression coverage around it.