Add configuration to increase or disable client RST_STREAM rate limiting

ASP.NET is rate-limiting client-initiated stream cancellation (i.e. RST_STREAM from the client). When it determines that the client is cancelling too many streams, it will start failing new streams with ENHANCE_YOUR_CALM. See discussion here: See https://github.com/dotnet/corefx/issues/40663#issuecomment-527611116

This makes it hard to perform stress testing, particularly with certain settings like low MaxStreamsPerConnection or high client cancellation rate.

It would be nice to add a setting to increase or disable the client cancellation rate limit.

Start with the linked corefx discussion and locate the ASP.NET Core HTTP/2 handling for client-initiated RST_STREAM cancellations and the existing rate-limit behavior. Determine where a configurable increase or disable option belongs, then verify that stress tests with low MaxStreamsPerConnection and frequent cancellations no longer receive unexpected ENHANCE_YOUR_CALM failures.

Written by the indexing model from the issue text.