mojom: move mojom/mojom_tool/generated -> mojom/generated. Update consumers

mojom/generated/README.md

 Generated  Files
 ==================
 
 The intermediate representation passed from the Mojom parser (the frontend
 of the Mojom compiler) to the code generators (the backend of the Mojom
 Compiler) is a `MojomFileGraph` described in  mojom_types.mojom and
 mojom_files.mojom in mojo/public/interfaces/bindings. Thus the Mojom compiler
 uses Mojo serialization to serialize the intermediate representation.
 
 This situation potentially entails a circular dependency because it means that
@@ skipping 15 matching lines @@
 
 ### Instructions for updating these files
 1) Make changes to mojom_types.mojom and mojom_files.mojom. This may be done
 either in the same patch as everything below or in its own initial patch.
 2) Compile these files to produce new generated files:
 ninja -C out/Debug mojo/public/interfaces/bindings.
 3) Copy the newly generated mojom_files.mojom.go and mojom_types.mojom.go
 into the appropriate locations in this directory.
 4) mojom_files.mojom.go needs to be manually patched in a minor way. In the
 import section at the top replace "mojo/public/interfaces/bindings/mojom_types"
-with "mojom/mojom_tool/generated/mojom_types".
+with "mojom/generated/mojom_types".
 5) Update the Go code in the serialization module of the parser to compensate
 for the changes if necessary. (Not necessary if the changes in step 1 were
 backward compatible.)
 6) Perform the analog of steps 3, 4, 5 for the Python code in the backend of
 the compiler. See
 mojo/public/tools/bindings/pylib/mojom/generate/generated/README.md
 for instructions.
 7) Land a patch containing your changes from steps 3 through 6.