Do not re-schedule request head timeout for HTTP/2 and HTTP/3

[aryan-25]

Motivation

Currently, in RequestTimeoutHandler, we reschedule the request timeout after seeing the request end part so that the timeout is ready for the next request on the channel:

swift-http-server/Sources/NIOHTTPServer/TimeoutHandlers.swift

Lines 133 to 136 in c2e1f5a

	// Re-arm the header timer so the next request on this connection is also protected.
	if let readHeaderTimeout {
	self.scheduleTimeout(readHeaderTimeout, context: context)
	}

However, this is only really necessary for HTTP/1. For HTTP/2 and HTTP/3, there can only ever be one request on a stream channel, so we do not need to reschedule the header timeout.

Avoiding this re-scheduling also means we can avoid the cost of cancelling the re-scheduled task (which is not required in the first place) when the handler is imminently removed after the request has finished.

Modifications

Introduced a new boolean flag named expectMultipleRequests to RequestTimeoutHandler. When expectMultipleRequests == false, the header timeout is not rescheduled after receiving a request end part.

Result

Unnecessary creation and cancellation of tasks avoided.