Direct: IdleTcpConnectionTimeout TimeSpan contract not honoring sub-second and fractional values (mirror of #4500)

## Description `IdleTcpConnectionTimeout` has the same silent truncation issue that was fixed for `OpenTcpConnectionTimeout` in #5873 (Fixes #4500). At `DocumentClient.cs:925`, the conversion is: ```csharp this.idleConnectionTimeoutInSeconds = (int)connectionPolicy.IdleTcpConnectionTimeout.Value.TotalSeconds; ``` This `(int)` cast silently truncates: - Sub-second values (e.g. `TimeSpan.FromMilliseconds(500)`) to 0 - Fractional values >= 1s (e.g. `TimeSpan.FromSeconds(10.5)`) down to the next whole second - Negative values to 0 Additionally, the public setter on `CosmosClientOptions.IdleTcpConnectionTimeout` does not validate for negative values. ## Expected behavior Apply the same contract as `OpenTcpConnectionTimeout` (per #5873): - Negative `TimeSpan` should throw `ArgumentOutOfRangeException` at the setter. - Sub-second values should normalize to 0 at the transport boundary. - Fractional values >= 1s should round up via `Math.Ceiling`. ## Related - #4500 (original issue for `OpenTcpConnectionTimeout`) - #5873 (fix PR for `OpenTcpConnectionTimeout`)