[halibobo1205]

What does this PR do?

Validates HTTP and JSON-RPC values assigned to protobuf string fields, rejecting unpaired surrogates. This aligns validation with the UTF-8 requirement enforced during gRPC/protobuf decoding.

Why are these changes required?

Malformed Unicode is currently accepted and replaced with ? during protobuf serialization. This change validates it explicitly during request handling.

Compatibility changes:

• Unpaired surrogates in protobuf string values now cause parsing or parameter errors instead of replacement.
• When packing a transaction, existing logic skips contract parameters that fail to parse; the subsequent result depends on the request's remaining checks.
• Well-formed Unicode, including emoji, and existing bytes field conversions remain unchanged.

This PR has been tested by:

• 610 HTTP and JSON-RPC tests pass locally on JDK 17, covering malformed surrogates, error reporting and valid Unicode.
• Before/after manual checks on a single-node private chain covered malformed strings and valid emoji through HTTP and JSON-RPC. Results matched the expected behavior.
• Multi-sign was not enabled on the private chain. gRPC was not tested manually.

Follow up

None.

Extra details

Only HTTP and JSON-RPC request handling changes. Transaction validation, transaction execution and block processing are unchanged.