[browser][wasm] Fix buffered symbol asset loading

[elringus]

This fixes SymbolsAsset.buffer handling in the browser runtime and adds a WBT regression test for buffered runtime assets:

• Fixed the browser loader so symbols assets supplied via buffer are handled correctly, instead of effectively requiring pendingDownload
• Kept the symbols path working with the existing text-based symbol map loading flow
• Added BufferedAssetsTest to WasmBasicTestApp that supplies these runtime assets via buffer:
  • dotnetwasm
  • assemblies
  • pdbs
  • symbols
• Added a matching ModuleConfigTests.BufferedAssetsTest integration test

The issue was discussed with @pavelsavara on .NET's Discord server.

Note: I was not able to run the browser test end-to-end in the local environment due local WBT/workload packaging setup issues. If anything fails on CI, I’ll follow up and fix the remaining issues there.

[Copilot]

Pull request overview

Fixes buffered symbols runtime asset loading in the browser WASM loader, and adds a regression scenario in WBT to exercise supplying runtime assets via asset.buffer.

Changes:

• Adjusted asset instantiation flow to correctly handle symbols assets when provided via buffer (and enabled buffered-response .text() decoding).
• Added a BufferedAssetsTest scenario to WasmBasicTestApp that assigns buffer for wasm/assemblies/pdbs/symbols during onConfigLoaded.
• Added a matching ModuleConfigTests.BufferedAssetsTest publish-and-run integration test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/mono/wasm/testassets/WasmBasicTestApp/App/wwwroot/main.js	Adds the BufferedAssetsTest scenario that supplies runtime assets via asset.buffer.
src/mono/wasm/Wasm.Build.Tests/ModuleConfigTests.cs	Adds an integration test that publishes and runs the new scenario (with symbol map emission enabled).
src/mono/browser/runtime/loader/assets.ts	Fixes loader handling for buffered symbols assets and implements .text() for buffered-response shim.

[elringus]

It seems the fingerprint stuff doesn't support file names with hashes. Is it somehow possible to generate the symbols file without the hash? Or maybe I should also patch the fingerprint resolver to ignore the hash on symbols?

Found unknown files in C:\helix\work\workitem\e\wbt artifacts\ModuleConfigTests_BufferedAssetsTest_Debug_False_0zxtutco_2je_鿀蜒枛遫䡫煉\App\bin\Debug\net11.0\publish\wwwroot_framework:
dotnet.native.8o3vuf3rfy.js.symbols
Add these to GetAllKnownDotnetFilesToFingerprintMap method

[dotnet-policy-service]

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