Perfetto Client API (4): Add initial integration test

Adds an initial integration test that coverse the basic case of
of an in-process data source and one session.
More will come in next CLs.

Bug: 132678367
Test: perfetto_integrationtest
Change-Id: I07e774e67c7842d78073e33c87dc658cd06d4616
diff --git a/BUILD.gn b/BUILD.gn
index 1e90be7..4a2c960 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -151,6 +151,7 @@
     deps = [
       "gn:default_deps",
       "gn:gtest_main",
+      "src/public:integrationtests",
       "src/traced/probes/ftrace:integrationtests",
       "test:end_to_end_integrationtests",
     ]