[Static web assets] Define static web asset endpoints in the SDK and generate an endpoints manifest

[javiercn]

Tracks dotnet/sdk#39636

• Introduces a StaticWebAssetEndpoint to represent the endpoints where any given static web asset must be available.
• Defines endpoints for all static web assets in the app.
  • Precomputes all the headers for all endpoints Content-Type, Content-Length, ETag, Last-Modified, Accept-Ranges
• Applies Content-Negotiation to compressed assets.
  • Maps the compressed assets to all the routes available to their respective related asset.
    • Duplicates the endpoints and points them to the compressed versions including Content-Encoding and Vary headers as well as a Content-Encoding selector that is used at runtime to disambiguate what asset to serve for an incoming request.
  • Updates compressed asset endpoints with Content-Encoding and Vary headers.

[javiercn]

dotnet/sdk#39636

[dyyhf123]

应该是 Vary: Accept-Encoding 吧，不理解 Vary: Content-Encoding 有什么作用