[Blazor] Generate Link headers based on StaticWebAssets manifest properties

[maraf]

Use properties generated on StaticWebAsset endpoints to generate Link headers.
The endpoint selection will be part of WebAssembly SDK.

The StaticWebAsset endpoint properties are following

• preloadgroup is used to identify assets to preload during WebAssembly component pre-rendering
• preloadrel is translated to rel attribute and defines relationship (preload or modulepreload are values that will be used for runtime assets)
• preloadas is translated to as attribute and specifies the type of content being loaded (script or fetch are values that will be used for runtime assets)
• preloadpriority is translated to fetchpriority attribute, is optional, and specifies the priority
• preloadcrossorigin is translated to crossorigin attribute (anonymous is the value that will be used for runtime assets)
• integrity is translated to integrity attribute and specifies the integrity of the asset
• preloadorder is used to sort headers based on priority

Example headers

Link: <_framework/dotnet.356opavw5k.js>; rel=preload; integrity="sha256-6bkzR9FAbZfpGpeWcvro3Cdv5q7Q3lrAcECLjdbxMSo="; as=script; fetchpriority=high; crossorigin=anonymous
Link: <_framework/dotnet.native.xcldtrkobb.js>; rel=preload; integrity="sha256-YXbaINTFw/gbCm/ArwBij7UxWCce5uzsMTB7SOFGGRk="; as=script; fetchpriority=high; crossorigin=anonymous
Link: <_framework/dotnet.runtime.bx28vfxjlk.js>; rel=preload; integrity="sha256-MVTbSi9B/7ru3wD2oGurO6Kdq3jzzwpgPjXBZtvxa0E="; as=script; fetchpriority=high; crossorigin=anonymous
Link: <_framework/dotnet.native.w3oqpgq65o.wasm>; rel=preload; integrity="sha256-dOqfsmWHK5+n/l/CjWWXK73okrrdc9sosIkU8QIcD8s="; as=fetch; fetchpriority=high; crossorigin=anonymous
Link: <_framework/System.Private.CoreLib.87qgib2l06.wasm>; rel=preload; integrity="sha256-pKbvr+/okd1TAIi+LQWskI1w2zrpPicTVP6Rk2FUfxs="; as=fetch; fetchpriority=low; crossorigin=anonymous
Link: <_framework/System.Runtime.InteropServices.JavaScript.uyv1n2071u.wasm>; rel=preload; integrity="sha256-Ftdgt1xNeQcttseov2QUsvHr9/ckGemptorEmOa16iQ="; as=fetch; fetchpriority=low; crossorigin=anonymous

Contributes #58875

[Copilot]

Pull Request Overview

This PR adds support for generating Link headers based on StaticWebAssets manifest properties for WebAssembly preloading. Key changes include:

• Propagation and handling of new preload-related properties in the resource collection resolver.
• Extension of endpoint rendering logic to append preload headers when using WebAssembly.
• Introduction of a new ResourcePreloadCollection class for grouping and ordering preload header values.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Shared/Components/ResourceCollectionResolver.cs	Added new string variables and updated AddResource to include preload attributes.
src/Components/Endpoints/test/EndpointHtmlRendererTest.cs	Added tests to verify correct generation and ordering of preload Link headers.
src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.Streaming.cs	Updated rendering logic to append WebAssembly preload headers conditionally.
src/Components/Endpoints/src/Builder/ResourcePreloadCollection.cs	Introduced new logic to build and order preload Link headers from resource assets.
src/Components/Endpoints/src/Builder/ResourceCollectionConvention.cs	Updated endpoint metadata conventions to include ResourcePreloadCollection.

[javiercn]

Should the order here "override" the fetch priority?

Also, rather than starting with a list, could we start already with a Dictionary<string, List> or something like that?

[maraf]

The idea is that within the same fetch priority, you can define the order, as throttling may apply

[javiercn]

Minor comments but it looks good