update_engine: Make InstallPlan's dump nicer

Its really hard to read anything out of the current InstallPlan's
logs. This CL makes it a bit more structured so it can be read easier.

Also added a few other properties of InstallPlan that were missing in
the Dump().

Added unittest for it too.

BUG=b:171829801
TEST=cros_workon_make --board reef --test update_engine

Change-Id: Iaa327e875877e9645ef8f0af875c280e11ee485d
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2558933
Tested-by: Amin Hassani <ahassani@chromium.org>
Auto-Submit: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
diff --git a/Android.bp b/Android.bp
index e5f8c31..a02b16f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -701,6 +701,7 @@
         "payload_consumer/file_descriptor_utils_unittest.cc",
         "payload_consumer/file_writer_unittest.cc",
         "payload_consumer/filesystem_verifier_action_unittest.cc",
+        "payload_consumer/install_plan_unittest.cc",
         "payload_consumer/partition_update_generator_android_unittest.cc",
         "payload_consumer/postinstall_runner_action_unittest.cc",
         "payload_consumer/verity_writer_android_unittest.cc",