[browser] [wasm] Make response streaming opt-out

[campersau]

Enabling response streaming is a breaking change because sync reads are no longer allowed and throw NotSupportedExceptions.
All supported browsers support response streaming.

To disable response streaming (and allow sync reads) set WebAssemblyEnableStreamingResponse to false:

request.Options.Set(new HttpRequestOptionsKey<bool>("WebAssemblyEnableStreamingResponse"), false);

Part of #77904

[lewing]

I support this in principle. I'm concerned about how the breaking change will surface to people upgrading. My assumption is that it at the moment it will only show up at runtime?

[campersau]

Yes, it will only show up at runtime. Similar to Kestrels AllowSynchronousIO defaulting to false.
The main issue I will have with dotnet/runtime types is that ZipArchive does not support async #1541 and would throw.
An other workaround is to buffer the stream manually.

Could we add an app context switch to toggle this globally?

[campersau]

Since all browsers support response streaming, should we remove BrowserHttpInterop.SupportsStreamingResponse?

• https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream#browser_compatibility
• https://developer.mozilla.org/en-US/docs/Web/API/Response#browser_compatibility

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing
See info in area-owners.md if you want to be subscribed.