Pineline key value parser does not support Chinese keys

## Expected Behavior
supports chinese key in pineline

## Current Behavior
missing key of chinese when parse in pineline

## Steps to Reproduce (for bugs)
my pinelines rules as follows:

```
rule "key value parser demo"
when
contains(to_string($message.message), "日志类型")
then
set_fields(
fields:
key_value(
value: to_string($message.message),
delimiters:" ",
trim_value_chars: "",
trim_key_chars:"",
kv_delimiters:"="
)
);
end
```

result:


## Environment

* Graylog Version: 4.2.9