Add crash diagnostics to device test pipeline step

## Context

PR #11224 migrates device tests from `RunTestApp` + NUnit XML + `RenameTestCases` to `dotnet test` + TRX. The old `CreateErrorResultsFile` in `RenameTestCases.cs` currently produces a "Possible Crash / {config}" synthetic test failure when no test results XML is found, but the error message provides no analysis of *why* the crash happened — just a raw logcat dump.

In [build 14010260](https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=14010260), the `Mono.Android.NET_Tests-NoAot` test failed with "Possible Crash / Release" because the emulator's `system_server` died mid-test (lowmemorykiller triggered, all system services died). Diagnosing this required manually downloading the logcat artifact and scanning thousands of lines for crash indicators.

## Proposal

After `dotnet test` completes (or crashes), add a pipeline step in `apk-instrumentation.yaml` that:

1. Only runs when the test step failed
2. Dumps `adb logcat -d` and scans for known crash patterns
3. Emits `##[warning]Crash indicator: ` messages so they appear directly in the AZDO build summary

### Crash patterns to detect

| Pattern | Message |
|---------|---------|
| `lowmemorykiller` or `lmkd` | Low memory killer triggered |
| Multiple `ServiceManager: service '...' died` | System services died (system_server likely crashed) |
| `FATAL EXCEPTION` | FATAL EXCEPTION in test process |
| `signal 11 (SIGSEGV)` or `signal 6 (SIGABRT)` | Native crash signal detected |
| `tombstoned: received crash request` | Tombstone generated (native crash) |
| `statsd.*system server restart` | system_server restarted |

### Benefits

- Crash diagnostics appear inline in the AZDO build log — no need to download artifacts
- Works regardless of test framework (NUnit, MTP, etc.)
- Shell-based, no C# changes required
- When the process is killed externally (e.g., emulator crash), on-device code can't report anything — the pipeline is the only reliable place to analyze what happened