Use '/protos/' as import prefix of perfetto protos

Historically we referred to our protos assuming
./protos as the source path. So all protos did
import "perfetto/trace/xxx.proto" and C++ code did
#include "perfetto/trace/xxx.pb(zero).h".
This CL makes everything relative to the repo root,
so now things look like
import "protos/perfetto/trace/xxx.proto", likewise
for #includes.
A lot of tooling out there (mainly bazel) seems to
assume that protos are referred to relatively from
the project root. Dealing with the current situation
seems prohibitively complex.

Bug: 140126865
Change-Id: I391aafaf276b68d3576ee16157dba0155dcb0879
diff --git a/src/traced/probes/probes_producer.cc b/src/traced/probes/probes_producer.cc
index cb1d1a4..3e08d6c 100644
--- a/src/traced/probes/probes_producer.cc
+++ b/src/traced/probes/probes_producer.cc
@@ -43,10 +43,10 @@
 #include "src/traced/probes/ps/process_stats_data_source.h"
 #include "src/traced/probes/sys_stats/sys_stats_data_source.h"
 
-#include "perfetto/trace/filesystem/inode_file_map.pbzero.h"
-#include "perfetto/trace/ftrace/ftrace_event_bundle.pbzero.h"
-#include "perfetto/trace/ftrace/ftrace_stats.pbzero.h"
-#include "perfetto/trace/trace_packet.pbzero.h"
+#include "protos/perfetto/trace/filesystem/inode_file_map.pbzero.h"
+#include "protos/perfetto/trace/ftrace/ftrace_event_bundle.pbzero.h"
+#include "protos/perfetto/trace/ftrace/ftrace_stats.pbzero.h"
+#include "protos/perfetto/trace/trace_packet.pbzero.h"
 
 namespace perfetto {
 namespace {