Update --show-stdout / --show-stderr help text to reflect LLM-aware default

[Evangelink]

Follow-up from #8771.

When running under a detected LLM/AI agent environment, the defaults for --show-stdout and --show-stderr flip from All to Failed (see TerminalOutputDevice.GetShowOutputMode). However, the option descriptions in PlatformResources.resx (TerminalShowStdoutOptionDescription, TerminalShowStderrOptionDescription) still hard-code:

Valid values are 'All', 'Failed', 'None'. Default is 'All'.

This means an LLM agent invoking --help sees misleading guidance about the very default that was changed for its benefit. The wording was intentionally not changed in #8771 to avoid 13-language XLF churn and keep that PR tight.

Suggested fix

Reword to something like:

Valid values are 'All', 'Failed', 'None'. Default is 'All' (or 'Failed' when an LLM/AI agent environment is detected).

This requires:

• Updating the two resource strings in src/Platform/Microsoft.Testing.Platform/Resources/PlatformResources.resx.
• Regenerating XLF files via dotnet msbuild src/Platform/Microsoft.Testing.Platform/Microsoft.Testing.Platform.csproj /t:UpdateXlf.
• Updating the wildcard expectations in:
  • test/IntegrationTests/Microsoft.Testing.Platform.Acceptance.IntegrationTests/HelpInfoTests.cs
  • test/IntegrationTests/Microsoft.Testing.Platform.Acceptance.IntegrationTests/HelpInfoAllExtensionsTests.cs
  • test/IntegrationTests/MSTest.Acceptance.IntegrationTests/HelpInfoTests.cs

Context

Tracked from review of #8771: #8771 (comment)