Timeout as TimeSpan, Support custom request timeout

[RomanSoloweow]

1. I think the current approach to use int for timeout is outdated and it generates a lot of errors when you need to remember that these are milliseconds, and you need translate it. Even HttpClient has timeout as TimeSpan.

2. The presence of "MaxTimeout" also confuses many users. If you want to set a custom timeout for the request, you need to remember which timeout is set for the rest client. Often, when you set a custom timeout for request, it's higher timeout than the default. These are requests for downloading and uploading files. It's rare case when the timeout is specially reduced for a particular request.

[RomanSoloweow]

@alexeyzimarev

tests failed again. Pull request does not affect this.

[RomanSoloweow]

@alexeyzimarev ping

[RomanSoloweow]

@alexeyzimarev ping

[alexeyzimarev]

I am not merging it because it will break things. Still thinking how to make it available with some transition.

[RomanSoloweow]

@alexeyzimarev any news?

[SergeiPavlov]

This change https://github.com/restsharp/RestSharp/pull/2078/files#diff-e00edb0ffd0c39411486e45e69f01fc071d99a607cd06c9e27acebdd1241939cR221

broke typical usage pattern new RestClient(sharedHttpClient,... because the HttpClient.Timeout property cannot be changed after HttpClient has started

[alexeyzimarev]

I noticed that one and flagged it, but for some reason I didn't think that ConfigureHttpClient is called when an external instance is used.

I will release a fix (the code is already fixed).

I think ConfigureHttpClient needs to be removed as all what's left there is setting Expect100Continue and it's a header.

[KonnectSalon]

Why do you guys keep removing things and break all dependencies that use different versions.