[gardening] vm-linux-release-x64, vm-appjit-linux-release-x64 and iso-stress-linux bots are broken

[aam]

The failures are due to broken concurrency stress tests.

https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket/8728721021758739937/+/u/test_results/new_test_failures__logs_

/=============================================================================================\
| vm/dart/isolates/concurrency_stress_sanity_test broke (Pass -> RuntimeError, expected Pass) |
\=============================================================================================/

--- Command "vm" (took 33.000634s):
DART_CONFIGURATION=ReleaseX64 out/ReleaseX64/dart --sound-null-safety -Dtest_runner.configuration=vm-linux-release-x64 --ignore-unrecognized-flags --packages=/b/s/w/ir/.dart_tool/package_config.json /b/s/w/ir/runtime/tests/vm/dart/isolates/concurrency_stress_sanity_test.dart

exit code:
255

stdout:
Running out/ReleaseX64/dart --packages=/b/s/w/ir/./.dart_tool/package_config.json --snapshot-kind=kernel --snapshot=/b/s/w/itzfxk6kid/OVPBAY/stress_test.dill /b/s/w/itzfxk6kid/OVPBAY/stress_test.dart

stderr:
../itzfxk6kid/OVPBAY/stress_test.dart:1231:8: Error: Error when reading 'tests/language/assert/initializer_const_function_runtime_test.dart': No such file or directory
import "/b/s/w/ir/runtime/tests/concurrency/../../../tests/language/assert/initializer_const_function_runtime_test.dart"
       ^
../itzfxk6kid/OVPBAY/stress_test.dart:1237:8: Error: Error when reading 'tests/language/assert/trailing_comma_runtime_test.dart': No such file or directory
import "/b/s/w/ir/runtime/tests/concurrency/../../../tests/language/assert/trailing_comma_runtime_test.dart"
       ^
../itzfxk6kid/OVPBAY/stress_test.dart:20691:15: Error: Method not found: 'main'.
      test613.main();
              ^^^^
../itzfxk6kid/OVPBAY/stress_test.dart:20754:15: Error: Method not found: 'main'.
      test616.main();
              ^^^^
Unhandled exception:
Expect.equals(expected: <0>, actual: <254>) fails.
#0      Expect._fail (package:expect/expect.dart:884:5)
#1      Expect._failNotEqual (package:expect/expect.dart:173:5)
#2      Expect.equals (package:expect/expect.dart:156:5)
#3      main.<anonymous closure> (file:///b/s/w/ir/runtime/tests/vm/dart/isolates/concurrency_stress_sanity_test.dart:57:12)
<asynchronous suspension>
#4      withTempDir (file:///b/s/w/ir/runtime/tests/vm/dart/snapshot_test_helper.dart:118:12)
<asynchronous suspension>
#5      main (file:///b/s/w/ir/runtime/tests/vm/dart/isolates/concurrency_stress_sanity_test.dart:26:3)
<asynchronous suspension>

--- Re-run this test:
python3 tools/test.py -n vm-linux-release-x64 vm/dart/isolates/concurrency_stress_sanity_test

This is due to https://dart.googlesource.com/sdk/+/6f66c12c05a5a83789cd382d62484e01ada1527f https://dart.googlesource.com/sdk/+/6cc9efe290f1f22932ee70b3244f695ba2f1163c that deleted test files referenced from runtime/tests/concurrency/stress_test_list.json

Previous such incidents were fixed by gardeners (https://dart.googlesource.com/sdk/+/cd7b1342bdf1bba84e2d683dbd8ffb040d4fa2ca).

cc @munificent

[munificent]

Fixed by https://dart-review.googlesource.com/c/sdk/+/400500.