System.Memory.Tests hangs after SearchValues_GetValues starts on MacCatalyst CoreCLR

### Description

`System.Memory.Tests` does not complete on MacCatalyst CoreCLR. In three independent x64 Helix attempts, the final unmatched test-start record was the empty-input case of `System.SpanTests.SpanTests.SearchValues_GetValues`; the app then remained running until the 75-minute XHarness timeout.

### Reproduction Steps

Run the full MacCatalyst CoreCLR libraries leg with per-test diagnostics enabled, as in [runtime-maccatalyst build 1540764](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1540764).

The final app record in all three x64 attempts was:

```text
[STRT][thread] System.SpanTests.SpanTests.SearchValues_GetValues(needle: "", byteNeedle: [])
```

No matching `[PASS]` or `[FAIL]` record, later test record, or test result file was produced.