Errors fail to marshal properly in traces

[CMajeri]

System information

Geth version: master?
OS & Version: Windows/Linux/OSX
Commit hash : 2faf796

Expected behaviour

I was running the debug_traceBlock rpc, when I noticed the errors were not displaying properly.

"error": {}

Actual behaviour

When I expected to see something like

"error": "out of gas"

After some digging, it seems the issue is with the fact that "Error" is an error interface in

type StructLogRes struct {
	Pc      uint64             `json:"pc"`
	Op      string             `json:"op"`
	Gas     uint64             `json:"gas"`
	GasCost uint64             `json:"gasCost"`
	Depth   int                `json:"depth"`
	Error   error              `json:"error,omitempty"`
	Stack   *[]string          `json:"stack,omitempty"`
	Memory  *[]string          `json:"memory,omitempty"`
	Storage *map[string]string `json:"storage,omitempty"`
}

Instead of something more marshallable like a string.
Since this struct is only used to marshal to json, maybe setting Error to be of type string, and setting it to Error.Error() could work?

Steps to reproduce the behaviour

Trace any block that has an error in a smart contract.

[rjl493456442]

@CMajeri Thanks for catching it! I have opened a PR to fix it. #23292