traceconv: niche decompress_packets option for rewriting a trace as if compressed_packets were written normally

I find myself wanting to convert the size breakdown of such traces to
pprof flamecharts once in a while, hence this helper.
The experimental proto path analysis in trace_processor already
understands compressed packets, but isn't as easy to get a pprof out of.

Change-Id: I3f203a591008e4078488f6acb89800beaf0e1055
diff --git a/Android.bp b/Android.bp
index a4b4894..636459a 100644
--- a/Android.bp
+++ b/Android.bp
@@ -12456,6 +12456,7 @@
         "src/traceconv/trace_to_profile.cc",
         "src/traceconv/trace_to_systrace.cc",
         "src/traceconv/trace_to_text.cc",
+        "src/traceconv/trace_unpack.cc",
     ],
 }