Handle server exception on wrong type in request

[JH23X]

Currently the http server shuts down when an argument is supplied as a wrong type in the request json. For example,
{"prompt": "Building a website can be done in 10 simple steps:","n_predict": 128, "stream": "false"}' (notice the "false" that is supplied as a string)
will cause the following exception on the server:

terminate called after throwing an instance of 'nlohmann::json_abi_v3_11_3::detail::type_error' {"tid": ...}
what(): [json.exception.type_error.302] type must be boolean, but is string
Aborted

The server shouldn't shut down from a malformed request. The proposed change catches this exception and logs a warning instead:
{"tid": ... ,"level":"WARN","function":"json_value","line":64,msg:"Wrong type supplied for parameter 'stream'. Expected 'b', using default value.","prompt":"Building a website can be done in 10 simple steps:","n_predict": 128,"stream":"false"}

Not 100% sure if this is the right way to go about this, so feel free to let me know of any changes you would like to see!

[phymbert]

Thanks, please wait for @ngxson review

[ngxson]

Maybe we can simply use LOG_WARNING here instead of calling directly server_log. But it's just a small detail, not important.