Use a controlled external origin in redirection tests

[ilonatommy]

Summary

• Add a test-owned server on a second ephemeral origin for external redirection tests.
• Configure component and non-Blazor redirect paths to use the controlled destination.
• Assert the exact destination URI and a marker from the loaded document.
• Unquarantine the seven external RedirectionTest variants.

Motivation

The tests previously redirected to microsoft.com and completed as soon as the browser URL contained that hostname. Because the Selenium browser is reused between theory rows, the external document could still be loading when the next row initialized. The next WebDriver command could then time out while reading the browser window size.

A test-owned second origin preserves the cross-origin behavior while removing dependencies on public DNS, TLS, CDN, redirects, and page-load timing.

RedirectStreamingEnhancedPostToExternal tested locally:
before the fix: 2/20
after the fix: 0/80

https://dev.azure.com/dnceng-public/public/_test/analytics?definitionId=87&contextType=build

Fixes #66969
Fixes #67342
Fixes #67738
Fixes #67444
Fixes #66969

[Copilot]

Pull request overview

This PR updates the Components E2E redirection tests to stop using microsoft.com as the external destination, replacing it with a test-owned second ephemeral origin to preserve cross-origin behavior while removing public network/page-load timing dependencies (addressing flakiness across multiple RedirectionTest variants).

Changes:

• Add a dedicated external-origin test server (ExternalNavigationStartup) and plumb its URI into the main test server via configuration.
• Update redirecting components/endpoints to navigate to the controlled external origin (including query-string behavior).
• Strengthen E2E assertions to validate the exact destination URI and confirm the external document is loaded (marker element), and unquarantine the external redirect variants.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Redirections/RedirectStreamingPost.razor	Uses configured external navigation target instead of hard-coded microsoft.com.
src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Redirections/RedirectStreamingGet.razor	Uses configured external navigation target instead of hard-coded microsoft.com.
src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Redirections/RedirectPost.razor	Uses configured external navigation target instead of hard-coded microsoft.com.
src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Redirections/RedirectGet.razor	Uses configured external navigation target instead of hard-coded microsoft.com.
src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Redirections/ExternalNavigationTarget.cs	New DI service that reads the external target URI from configuration and constructs a stable “URI + query” value.
src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs	Registers ExternalNavigationTarget and routes non-Blazor external redirects to the controlled target.
src/Components/test/testassets/Components.TestServer/ExternalNavigationStartup.cs	New minimal external-origin server that serves a marker element to assert page-load completion.
src/Components/test/E2ETest/ServerRenderingTests/RedirectionTest.cs	Starts a second-origin server fixture, configures the main server to redirect to it, improves assertions, and unquarantines external variants.

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[ilonatommy]

/ba-g failures not connected