Avoid disposing invalid handle in HttpSys server close

[BrennanConroy]

Avoid disposing invalid handle in HttpSys server close

Description

HttpSys docs say we should close the request queue with HttpCloseRequestQueue and not with CloseHandle. So the PR #61325 noticed this while making an unrelated change and updated the code to call HttpCloseRequestQueue. Unfortunately, we kept the old Handle.Dispose() code which is effectively a double free.

The fix is to mark the handle as invalid after closing the request queue so we avoid the double free.

Fixes #65259

Customer Impact

Error log (and exception from Dispose) when cleaning up HttpSys server.
Issue: #65259

Regression?

• Yes
• No

Regressed in #61325 (10.0-p5)

Risk

• High
• Medium
• Low

Customer reported exception was easy to repro and thus easy to verify it was fixed with the change.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[Copilot]

Pull request overview

Fixes a regression in the HttpSys server shutdown path by preventing a double-close of the request queue handle after switching to HttpCloseRequestQueue, aligning handle lifecycle management with Http.Sys API requirements.

Changes:

• Keep HttpCloseRequestQueue(Handle) as the authoritative close operation for the request queue.
• Prevent a subsequent SafeHandle.Dispose() from attempting to close the same native handle by marking the handle invalid after closing.
• Add clarifying comments about disposal order relative to ThreadPoolBoundHandle.

[Copilot]

After Handle.SetHandleAsInvalid(), consider still calling Handle.Dispose() to suppress the SafeHandle finalizer and release managed resources; disposal should be a no-op for the native handle once it’s marked invalid.

Suggested change

	Handle.SetHandleAsInvalid();
	Handle.SetHandleAsInvalid();
	Handle.Dispose();

[dotnet-policy-service]

Hi @@BrennanConroy. This PR was just approved to be included in the upcoming servicing release. Somebody from the @dotnet/aspnet-build team will get it merged when the branches are open. Until then, please make sure all the CI checks pass and the PR is reviewed.