This sets the default executable for the test reporter to `bin/rails`
instead of just `rails`.  This only affects command output messages.

__Before__

  ```console
  $ bin/rails test --help
  Usage: rails test [options] [files or directories]

  You can run a single test by appending a line number to a filename:

      rails test test/models/user_test.rb:27

  You can run multiple files and directories at the same time:

      rails test test/controllers test/integration/login_test.rb

  By default test failures and errors are reported inline during a run.

  minitest options:
  ...

  $ bin/rails test test/my_failing_test.rb
  Running 1 tests in a single process (parallelization threshold is 50)
  Run options: --seed 20964

  # Running:

  F

  Failure:
  MyFailingTest#test_it_fails [.../test/my_failing_test.rb:5]:
  Epic Fail!

  rails test test/my_failing_test.rb:4

  Finished in 0.185761s, 5.3833 runs/s, 5.3833 assertions/s.
  1 runs, 1 assertions, 1 failures, 0 errors, 0 skips
  ```

__After__

  ```console
  $ bin/rails test --help
  Usage: bin/rails test [options] [files or directories]

  You can run a single test by appending a line number to a filename:

      bin/rails test test/models/user_test.rb:27

  You can run multiple files and directories at the same time:

      bin/rails test test/controllers test/integration/login_test.rb

  By default test failures and errors are reported inline during a run.

  minitest options:
  ...

  $ bin/rails test test/my_failing_test.rb
  Running 1 tests in a single process (parallelization threshold is 50)
  Run options: --seed 34270

  # Running:

  F

  Failure:
  MyFailingTest#test_it_fails [.../test/my_failing_test.rb:5]:
  Epic Fail!

  bin/rails test test/my_failing_test.rb:4

  Finished in 0.228461s, 4.3771 runs/s, 4.3771 assertions/s.
  1 runs, 1 assertions, 1 failures, 0 errors, 0 skips
  ```

__Diff__

  ```diff
  @@ -1,13 +1,13 @@
   $ bin/rails test --help
  -Usage: rails test [options] [files or directories]
  +Usage: bin/rails test [options] [files or directories]

   You can run a single test by appending a line number to a filename:

  -    rails test test/models/user_test.rb:27
  +    bin/rails test test/models/user_test.rb:27

   You can run multiple files and directories at the same time:

  -    rails test test/controllers test/integration/login_test.rb
  +    bin/rails test test/controllers test/integration/login_test.rb

   By default test failures and errors are reported inline during a run.

  @@ -26,7 +26,7 @@
   MyFailingTest#test_it_fails [.../test/my_failing_test.rb:5]:
   Epic Fail!

  -rails test test/my_failing_test.rb:4
  +bin/rails test test/my_failing_test.rb:4

   Finished in 0.185761s, 5.3833 runs/s, 5.3833 assertions/s.
   1 runs, 1 assertions, 1 failures, 0 errors, 0 skips
  ```