[CI Failure] Flaky: EnvironmentCheckerTests.CheckAllAsync_TimedOutCheckReportsWarningAndContinues - check completes too slowly under CI load

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/31066050322
Build error leg or test failing: Tests / Cli / Cli (windows-latest) / `Aspire.Cli.Tests.Utils.EnvironmentCheckerTests.CheckAllAsync_TimedOutCheckReportsWarningAndContinues`
Pull request: #18986

## Error Message

```
Assert.Collection() Failure: Item comparison failure
Expected: EnvironmentCheckResult { Message = "Completed", ... }
Actual: EnvironmentCheckResult { Message = "Environment check 'test-environment' timed out aft"..., ... }
at Aspire.Cli.Tests.Utils.EnvironmentCheckerTests.CheckAllAsync_TimedOutCheckReportsWarningAndContinues() in ...\EnvironmentCheckerTests.cs:line 55
```

## Description

Flaky: EnvironmentCheckerTests.CheckAllAsync_TimedOutCheckReportsWarningAndContinues - check completes too slowly under CI load

**Type**: flaky-test

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-08-06 | [31066050322](https://github.com/microsoft/aspire/actions/runs/31066050322) | Tests / Cli / Cli (windows-latest) | #18986 |
| 2026-08-31 | [33434427094](https://github.com/microsoft/aspire/actions/runs/33434427094) | Tests / Cli / Cli (macos-latest) | #19727 |
| 2026-09-11 | [34655355873](https://github.com/microsoft/aspire/actions/runs/34655355873) | Tests / No-package tests (collection, Aspire.Hosting.Tests, Hosting-4, Hosting-4, tests/Aspire.Hosting.Tests) / Hosting-4 (windows-latest) | #20072 |
| 2026-09-14 | [34815567672](https://github.com/microsoft/aspire/actions/runs/34815567672) | Tests / No-package tests (regular, Aspire.Cli.Tests, Cli, Cli, tests/Aspire.Cli.Tests/Aspire.Cli.Tests.cs... / Cli (macos-latest) | #18763 |

Start with Aspire.Cli.Tests.Utils.EnvironmentCheckerTests.CheckAllAsync_TimedOutCheckReportsWarningAndContinues at line 55, then run the named test on Windows or macOS to reproduce the CI-only timing failure. Compare the expected Completed result with the timeout warning and inspect the test's timing assumptions. Done means the test reliably reports the completed check and continues under CI load.

Written by the indexing model from the issue text.