Enhance TimerFileDescriptor to schedule multiple tasks

Improved the class to allow scheduling and execution of multiple tasks
concurrently.

Test: TH
Change-Id: I79b63c6846e0e0a934f257d4a38d9cab08bd13e8
diff --git a/staticlibs/tests/unit/Android.bp b/staticlibs/tests/unit/Android.bp
index 9d1d291..f4f1ea9 100644
--- a/staticlibs/tests/unit/Android.bp
+++ b/staticlibs/tests/unit/Android.bp
@@ -28,6 +28,7 @@
         "net-utils-device-common-struct-base",
         "net-utils-device-common-wear",
         "net-utils-service-connectivity",
+        "truth",
     ],
     libs: [
         "android.test.runner.stubs",