Bazel: Move include paths to libraries

Instead of having a global list of -I include paths, have each library
provide a -I for the public/ directory using the includes argument.

Change-Id: I2e321752906920cd94beaaab97b8796af85078e4
diff --git a/pw_bloat/BUILD b/pw_bloat/BUILD
index d0e93fc..f0911f9 100644
--- a/pw_bloat/BUILD
+++ b/pw_bloat/BUILD
@@ -28,6 +28,7 @@
     name = "bloat_this_binary",
     srcs = ["bloat_this_binary.cc"],
     hdrs = ["public/pw_bloat/bloat_this_binary.h"],
+    includes = ["public"],
 )
 
 # Standard minimal base binary for bloat reports.