[HybridWebView] Properly managed response streams

[mattleibow]

Description of Change

The main issue that this PR fixes is the case where we write to a stream using a StreamWriter, which is then disposed causing the stream to be disposed as well.

Instead of just leaving the stream open, I refactored the writing code to not copy so many times. Before we would copy from the source stream into a MemoryStream and then into a InMemoryRandomAccessStream. I now use the extension method to wrap the InMemoryRandomAccessStream in a Stream and write directly.

I also cache the 404 message and write the bytes directly instead of first converting/copying to a stream.

Issues Fixed

Fixes #27953

PR Overview

This PR refactors the response stream handling in HybridWebView to reduce unnecessary stream copies and ensure the 404 response is managed more efficiently while adding a relevant test.

• Refactored stream handling in Windows-specific HybridWebView handler to use IBuffer directly instead of multiple MemoryStream copies.
• Introduced a lazy-loaded cached 404 message buffer to optimize error responses.
• Added new test cases in HybridWebViewTests to check file request statuses via JavaScript.

Reviewed Changes

File	Description
src/Controls/tests/DeviceTests/Elements/HybridWebView/HybridWebViewTests.cs	Added new test "RequestFileFromJS" with InlineData to validate response statuses.
src/Core/src/Handlers/HybridWebView/HybridWebViewHandler.Windows.cs	Refactored stream copying methods and added a lazy-loaded 404 message buffer to streamline response handling.

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

[mattleibow]

This was the main issue. The writer will also dispose the stream.

[tj-devel709]

LGTM

[jsuarezruiz]

Both methods have similar logic for creating an InMemoryRandomAccessStream, could we refactor it creating a helper method?

private static async Task<IRandomAccessStream> CreateRandomAccessStreamAsync(Func<IRandomAccessStream, Task> writeContentAsync)
{
	var ras = new InMemoryRandomAccessStream();
	await writeContentAsync(ras);
	await ras.FlushAsync();
	ras.Seek(0);
	return ras;
}