* Added support for authentication codes for the VM service.

Previously, a valid web socket connection would use the following URI:

`ws://127.0.0.1/ws`

Now, by default, the VM service requires a connection to be made with a
URI similar to the following:

`ws://127.0.0.1:8181/Ug_U0QVsqFs=/ws`

where `Ug_U0QVsqFs` is an authentication code generated and shared by
the
service.

This behavior can be disabled with the `--disable-service-auth-codes`
flag.

Updates gradle.

This reverts commit d07c09c9a1a8bd9a0860c579154974437da14024.

This reverts commit 93573de2.

Fails in the devicelab:

```
run:stderr: A problem occurred evaluating project ':app'.
run:stderr: > Could not resolve all files for configuration 'classpath'.2018-10-23T10:46:46.335864:
run:stderr:    > Could not find aapt2-proto.jar (com.android.tools.build:aapt2-proto:0.3.1).2018-10-23T10:46:46.335960:
run:stderr:      Searched in the following locations:2018-10-23T10:46:46.336048:
```

Adds an integration devicelab test that runs an Android app with two
custom named isolates. Tests that the isolate names are present and that
it's possible to attach to just one of the isolates.

Fixes flutter/flutter#22009