Enable artifact processing for truncated test runs

[Evangelink]

Summary

• allow policy-truncated dotnet test runs to invoke artifact processors that explicitly advertise truncated-run support
• pass maximumFailedTests or timeout through the dispatcher manifest while preserving unconditional skips for help, discovery, explicit opt-out, and Ctrl+C
• consume dispatcher provenance so only represented inputs are replaced, with a compatibility fallback for older hosts
• document the behavior and add planner, manager, protocol, handler, telemetry, and end-to-end coverage

Validation

• build.cmd
• focused artifact post-processing dotnet.Tests: 79 passed
• focused TestApplicationHandlerTests: 29 passed

Related: microsoft/testfx#10414

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