Shared API's V2 (#289)

Added V2 Shared API's infrastructure
Added request coalescing
Added rate limiting admission logic
Fixed some rate limiting issues

CryptoExchange.Net/SharedApis/Legacy/Rest/Futures/IFundingRateRestClient.cs

@@ -0,0 +1,27 @@
+using CryptoExchange.Net.Objects;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace CryptoExchange.Net.SharedApis
+{
+    /// <summary>
+    /// Client for request funding rate records
+    /// </summary>
+    public interface IFundingRateRestClient : ISharedClient
+    {
+        /// <summary>
+        /// Funding rate request options.<br />
+        /// Use <see cref="CapabilityOptions.RequiredExchangeParameters"/> and <see cref="CapabilityOptions.OptionalExchangeParameters"/> to check for required and optional parameters for the request. <br />
+        /// Exchange specific parameters can be added to the request via the `ExchangeParameters` property of the request object.
+        /// </summary>
+        GetFundingRateHistoryOptions GetFundingRateHistoryOptions { get; }
+        /// <summary>
+        /// Get funding rate records, see <see cref="GetFundingRateHistoryOptions"/> for request options and exchange specific required/optional parameters. <br />
+        /// The result is paginated, if there are more results to be retrieved, the `NextPageRequest` property of the result will contain the pagination request to be used for the next request to continue pagination.
+        /// </summary>
+        /// <param name="request">Request info</param>
+        /// <param name="nextPageToken">The pagination request from the previous request result `NextPageRequest` property to continue pagination</param>
+        /// <param name="ct">Cancellation token</param>
+        Task<HttpResult<SharedFundingRate[]>> GetFundingRateHistoryAsync(GetFundingRateHistoryRequest request, PageRequest? nextPageToken = null, CancellationToken ct = default);
+    }
+}