Test Orchestrator fails with "No test results."

### Description
If tests are run with AndroidX test orchestrator, every test run fails with `Test running failed: No test results`.

### Steps to Reproduce
1. Create empty AS project.
2. Insert attached `build.gradle`
3. Run ExampleInstrumentedTest (or any test...)

### Expected Results
Tests should run with given options. They only run if AndroidX Orchestrator is disabled.

### Actual Results
Log:
> 020-09-21 10:41:29.802 7943-7943/? E/appproc: ERROR: could not find class 'androidx.test.services.shellexecutor.ShellMain'
2020-09-21 10:41:29.802 7943-7943/? A/app_process: java_vm_ext.cc:570] JNI DETECTED ERROR IN APPLICATION: JNI NewGlobalRef called with pending exception java.lang.ClassNotFoundException: androidx.test.services.shellexecutor.ShellMain
2020-09-21 10:41:29.802 7943-7943/? A/app_process: java_vm_ext.cc:570] (Throwable with empty stack trace)
2020-09-21 10:41:29.802 7943-7943/? A/app_process: java_vm_ext.cc:570]
2020-09-21 10:41:29.802 7943-7943/? A/app_process: java_vm_ext.cc:570] in call to NewGlobalRef
2020-09-21 10:41:29.832 7943-7943/? A/app_process: runtime.cc:630] Runtime aborting...

### AndroidX Test and Android OS Versions

> androidTestImplementation 'androidx.test.ext:junit:1.1.2'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
androidTestImplementation 'androidx.test:Runner:1.3.0'
androidTestUtil 'androidx.test:orchestrator:1.3.0'
compileSdkVersion 29
buildToolsVersion "29.0.3"

Full app-level [build.gradle.txt](https://github.com/android/android-test/files/5254648/build.gradle.txt) is attached.

Occured on emulators with Oreo and v10 + physical device on v10.

Reproduce the failure with the attached build.gradle and an ExampleInstrumentedTest using AndroidX Test Orchestrator. Start by tracing the missing androidx.test.services.shellexecutor.ShellMain dependency from the reported log; done means instrumented tests run successfully with the listed orchestrator options.

Written by the indexing model from the issue text.