Support arbitrary number of TRACE_EVENT arguments.

Refactor handling of TRACE_EVENT arguments to support passing an arbitrary
number of debug annotations, as well as passing debug annotations together
with a lambda.

This refactoring provides the basis for the future support of multiple
lambdas, as well as lambdaless filling of typed trace arguments.

The necessary logic is encapsulated in a separate file, which ensures
that the Chromium implementation of typed macros can reuse it without
waiting for the client library migration.

Bug: b/184558843
Change-Id: I1cd62b7a8b40a6916ba66834c7815cf045793064
diff --git a/BUILD b/BUILD
index d9e430a..322f281 100644
--- a/BUILD
+++ b/BUILD
@@ -528,6 +528,7 @@
         "include/perfetto/tracing/internal/track_event_data_source.h",
         "include/perfetto/tracing/internal/track_event_internal.h",
         "include/perfetto/tracing/internal/track_event_macros.h",
+        "include/perfetto/tracing/internal/write_track_event_args.h",
         "include/perfetto/tracing/locked_handle.h",
         "include/perfetto/tracing/platform.h",
         "include/perfetto/tracing/string_helpers.h",