Flake: spanner emulator crashed?

https://pantheon.corp.google.com/cloud-build/builds;region=us-central1/1bc9bf43-24a8-4a52-8ec1-4881c6481668;step=3?project=rust-sdk-testing

I cancelled the build, but if I had to guess, I'd say the emulator crashed.

```
running 14 tests
test spanner::run_directed_read_tests ... ok
test spanner::run_query_tests ... FAILED
test spanner::run_partitioned_dml_tests ... FAILED
test spanner::run_batch_write_tests ... FAILED
test spanner::run_batch_read_only_transaction_tests ... FAILED
test spanner::run_pg_dialect_tests ... FAILED
test spanner::run_batch_dml_tests has been running for over 60 seconds
test spanner::run_concurrent_inline_begin_tests has been running for over 60 seconds
test spanner::run_read_only_transaction_options_tests has been running for over 60 seconds
test spanner::run_read_tests has been running for over 60 seconds
test spanner::run_read_write_tests has been running for over 60 seconds
test spanner::run_read_write_transaction_options_tests has been running for over 60 seconds
test spanner::run_write_only_transaction_options_tests has been running for over 60 seconds
test spanner::run_write_tests has been running for over 60 seconds
test spanner::run_read_tests ... FAILED
test spanner::run_read_write_tests ... FAILED
test spanner::run_read_write_transaction_options_tests ... FAILED
test spanner::run_write_only_transaction_options_tests ... FAILED
test spanner::run_write_tests ... FAILED
```

Start with the linked Cloud Build run and the Spanner test output, then inspect the emulator logs for the failures and tests that hang. Reproduce the run to determine whether the emulator crashed; done means the affected Spanner test suite completes without failures or hangs.

Written by the indexing model from the issue text.