Add missing RPC examples to autogenerate-rpc-examples script for improved API documentation

Our current API documentation generation process automatically produces reference documentation for all RPC methods. However, many RPC endpoints are missing request/response examples, making it difficult for developers to understand how to use them correctly.

### Missing Examples
The following RPC endpoints currently lack examples in tests/autogenerate-rpc-examples.py.
- currencyconvert
- splicein
- createproof
- clnrest-register-path
- sendamount
- graceful
- askrene-remove-channel-update
- currencyrate
- spliceout
- askrene-bias-node
- bkpr-report
- xkeysend
- listcurrencyrates
- delnetworkevent
- cancelrecurringinvoice
- listnetworkevents
- injectonionmessage

Remove above RPCs from `IGNORE_RPCS_LIST` and add their example calls in the script to include example request/response pairs for each RPC method.