tp: add config objects for trace processor and batch trace processor

This CL removes ad-hoc parameters being passed to contructor to instead
passing a config object which can override various functionality: this
will replace loader_vendor once G3 migrates to using just this.

Change-Id: Ibbf3960106726a00cb332bb3043b75e00681a324
Bug: 180499808
diff --git a/CHANGELOG b/CHANGELOG
index 19f75ba..c931c67 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -2,7 +2,13 @@
   Tracing service and probes:
     *
   Trace Processor:
-    *
+    * The argument for the trace path in constructor of TraceProcessor
+      in the Python API taks |trace| is renamed from |file_path| to |trace|.
+      |file_path| is deprecated and may be removed in the future.
+    * The Python API now takes a TraceProcessorConfig in the constructor
+      instead of passing parameters directly. This may break existing code
+      but migration should be trivial (all current options are still
+      supported).
   UI:
     *
   SDK: