StdoutLogger: support log level

[nurzhan-saktaganov]

Add new structure that writes to Stdout and supports log level, example:

type StdoutLogLevel int

const (
    StdoutLogDebug StdoutLogLevel = iota
    StdoutLogInfo
    StdoutLogWarn
    StdoutLogError
)

type StdoutLoggerf struct{
    LogLevel StdoutLogLevel
}