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

mojom/mojom_tool/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
-in  order to build the Mojom compiler it is necessary to use code that has been
-generated by the Mojom compiler. In order to break this circular dependency we
-check in the generated code needed by the compiler rather than generating it
-while building the compiler.
-
-This directory contains the checked-in generated Go code used by the frontend
-of the compiler:
-mojom_files/mojom_files.mojom.go and
-mojom_types/mojom_types.mojom.go.
-
-The backend of the Mojom compiler is  written in Python and the corresponding
-generated Python files may be found in
-mojo/public/tools/bindings/pylib/mojom/generate/generated/mojom_files_mojom.py
-and
-mojo/public/tools/bindings/pylib/mojom/generate/generated/mojom_types_mojom.py
-
-### 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".
-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.