[browser][WBT] EventPipe - end to end test

[pavelsavara]

• CPU samples
• GC heap dump
• metrics

Fixes #115930

[pavelsavara]

Log

Totals
     6,590 events.
     6,449 events with stack traces.
         0 events with code addresses in them.
   139,606 total code address instances. (stacks or other)
     1,017 unique code addresses. 
     2,664 unique stacks.
       431 unique managed methods parsed.
     7,168 CLR method event records.
[Conversion complete 6,590 events.  Conversion took 0 sec.]

[Copilot]

Pull Request Overview

This PR adds end-to-end tests verifying EventPipe functionality for CPU samples, GC heap dumps, and metrics in a Blazor WebAssembly test app. Key changes include:

• Introducing a runtime configuration for browser with host properties.
• Adding a conditional PackageReference and a file upload endpoint in DevServerStartup.
• Implementing new EventPipe diagnostics tests with updated timeout and validation options.

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
App/BlazorBasicTestApp.runtimeconfig.json	Added runtime configuration for browser host properties.
App/BlazorBasicTestApp.csproj	Updated PackageReference with a condition for DEVSERVER.
host/DevServer/DevServerStartup.cs	Added file upload endpoint to facilitate test trace uploads.
Wasm.Build.Tests.csproj	Added dependency on Microsoft.Diagnostics.Tracing.TraceEvent.
Wasm.Build.Tests/Templates/WasmTemplateTestsBase.cs	Updated timeout logic in WaitForExitMessageAsync.
Wasm.Build.Tests/BrowserStructures/RunOptions.cs	Introduced TimeoutSeconds property with default value.
Wasm.Build.Tests/Blazor/EventPipeDiagnosticsTests.cs	Added tests for CPU samples, metrics, and GC heap dump validations.
Wasm.Build.Tests/Blazor/BlazorRunOptions.cs	Propagated TimeoutSeconds to the run options.
diagnostics/diagnostics-js.ts	Added a runtime check to prevent multiple diagnostic clients.
eng/testing/scenarios/BuildWasmAppsJobsList.txt	Updated job list to include EventPipe diagnostics tests.