Add Percent property to express thresholds

[AntyaDev]

AC:

• Extend contracts by Percent property for Request and StatusCodes

type RequestStats = {
    Count: int
    RPS: float
    Percent: int
}

type StatusCodeStats = {
    StatusCode: string
    IsError: bool
    Message: string
    Count: int
    Percent: int
}

• Implement the logic for percent calculation to allow users to express thresholds

stats.Ok.Request.Percent == 80   // success rate = 80%
stats.Fail.Request.Percent == 20 // error rate = 20%

stats.Ok.StatusCodes.Get("200").Percent >= 50)   // 50% requests with status code 200
stats.Fail.StatusCodes.Get("500").Percent == 25) // 25% requests with status code 500
stats.Fail.StatusCodes.Get("501").Percent == 25) // 25% requests with status code 501