Move policy generated files to components/policy

Previously these were generated in a "policy" toplevel directory. Generally
components should use the GN target_gen_dir for the generated files for
consistency.

policy_proto_export.h was moved to the proto directory. DEPS files were updated
(a few rules were broadened to all of components/policy since listing
individual headers in DEPS is not helpful and makes it more difficult for
others down the road).

The rest of the changes are mechanical search-and-replace for the new paths.

TBR=dbeam for chrome/browser/ui/webui

Review-Url: https://codereview.chromium.org/2273783002
Cr-Commit-Position: refs/heads/master@{#414094}
diff --git a/remoting/host/policy_watcher.cc b/remoting/host/policy_watcher.cc
index ea90d63..d8bc0561 100644
--- a/remoting/host/policy_watcher.cc
+++ b/remoting/host/policy_watcher.cc
@@ -23,7 +23,7 @@
 #include "components/policy/core/common/policy_service_impl.h"
 #include "components/policy/core/common/schema.h"
 #include "components/policy/core/common/schema_registry.h"
-#include "policy/policy_constants.h"
+#include "components/policy/policy_constants.h"
 #include "remoting/host/dns_blackhole_checker.h"
 #include "remoting/host/third_party_auth_config.h"
 #include "remoting/protocol/port_range.h"