UiDevice.executeShellCommand doesn't support full adb shell functionality

### Description

`UiDevice.executeShellCommand` doesn't have an affordance for stdin, and doesn't allow piping between multiple commands, or redirects.

### Steps to Reproduce

```
// The following line will fail:
assertEquals("foo\n", mUiDevice.executeShellCommand("echo foo | xargs echo $1"))
```

### AndroidX Test and Android OS Versions

uiautomator 2.2.0, any supported (example above requires API 26, due to `xargs` usage)

### Proposal

I worked around this (in the Jetpack repo) by adding an extension - [`UiDevice.executeShellScript(script: String, stdin: String? = null)`](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-master-dev:benchmark/perfetto/src/main/java/androidx/benchmark/perfetto/ShellUtils.kt;l=37;drc=2193701d13f8c18dc3540a3c5e6f34cb93fae6cc)

Would you be interested in accepting this functionality upstream?

It works by writing the 'script' param to a shell-readable location, copying it to a shell-runnable location (needed in Q+), and executing it there. As this adds additional binder calls, I think it makes sense to add it as a separate method. Can also as part of this link to [Android's shell and utilities](https://android.googlesource.com/platform/system/core/+/master/shell_and_utilities/README.md#) from the docs of both methods, as that's a *very* necessary reference for running shell commands on Android.

Inizia individuando UiDevice.executeShellCommand e confronta il suo comportamento con l’implementazione di ShellUtils.kt a cui si fa riferimento. Riproduci quindi l’esempio di pipeline documentato, poi determina come esporre e documentare lo script proposto e il supporto opzionale a stdin, includendo il riferimento alle utilità shell di Android. Il lavoro è completo quando gli script shell possono usare stdin, pipe e redirezioni tramite l’upstream API.

Scritto dal modello di indicizzazione a partire dal testo della issue.