Add support for custom listeners in instrumentation tests

Summary:
This adds the ability for adding custom listeners that allow instrumentation tests to also execute code as part of the host. This is useful for a few cases.
1. Allow the test to run some custom adb commands prior to executing the test.
2. Perform privileged actions such as communicating with WWW as the host doesn't have access to the server.

This only supported on buck2, I do not intend to bring this to buck1.

Differential Revision: D51141856

fbshipit-source-id: 3050b29dfc315d2e1731190c25dffda1ad282f3a

prelude/android/android.bzl

@@ -143,6 +143,8 @@ extra_attributes = {
         "_java_toolchain": toolchains_common.java_for_android(),
     },
     "android_instrumentation_test": {
+        "instrumentation_test_listener": attrs.option(attrs.source(), default = None),
+        "instrumentation_test_listener_class": attrs.option(attrs.string(), default = None),
         "_android_toolchain": toolchains_common.android(),
         "_exec_os_type": buck.exec_os_type_arg(),
         "_java_toolchain": toolchains_common.java_for_android(),

prelude/android/android_instrumentation_test.bzl

@@ -24,7 +24,10 @@ def android_instrumentation_test_impl(ctx: AnalysisContext):
 
     classpath_args = cmd_args()
     classpath_args.add("-classpath")
-    classpath_args.add(cmd_args(classpath, delimiter = get_path_separator_for_exec_os(ctx)))
+    extra_classpath = []
+    if ctx.attrs.instrumentation_test_listener != None:
+        extra_classpath.append(ctx.attrs.instrumentation_test_listener)
+    classpath_args.add(cmd_args(classpath + extra_classpath, delimiter = get_path_separator_for_exec_os(ctx)))
     classpath_args_file = ctx.actions.write("classpath_args_file", classpath_args)
     cmd.append(cmd_args(classpath_args_file, format = "@{}").hidden(classpath_args))
 
@@ -52,7 +55,6 @@ def android_instrumentation_test_impl(ctx: AnalysisContext):
         test_runner_file.as_output(),
     ])
     ctx.actions.run(manifest_utils_cmd, category = "get_manifest_info")
-
     cmd.extend(
         [
             "--test-package-name",
@@ -64,6 +66,9 @@ def android_instrumentation_test_impl(ctx: AnalysisContext):
         ],
     )
 
+    if ctx.attrs.instrumentation_test_listener_class != None:
+        cmd.extend(["--extra-instrumentation-test-listener", ctx.attrs.instrumentation_test_listener_class])
+
     cmd.extend(
         [
             "--adb-executable-path",