tp: create perfetto_sql folder and rejig various modules

This CL introduces a top level "perfetto_sql" folder to trace processor
and moves the prelude, intrinsics, stdlib and engine components into it.
Follow up work will rework the documentation to expose this grouping of
components to public.

Change-Id: I35bea692fc5c95999e3991c9952511edd4bf054b

src/trace_processor/iterator_impl.cc

diff --git a/src/trace_processor/iterator_impl.cc b/src/trace_processor/iterator_impl.cc
index b859c57..4b3e997 100644
--- a/src/trace_processor/iterator_impl.cc
+++ b/src/trace_processor/iterator_impl.cc
@@ -18,7 +18,7 @@
 
 #include "perfetto/base/time.h"
 #include "perfetto/trace_processor/trace_processor_storage.h"
-#include "src/trace_processor/sqlite/perfetto_sql_engine.h"
+#include "src/trace_processor/perfetto_sql/engine/perfetto_sql_engine.h"
 #include "src/trace_processor/sqlite/scoped_db.h"
 #include "src/trace_processor/storage/trace_storage.h"
 #include "src/trace_processor/trace_processor_impl.h"