Please rename protobuf field "module" to "gate_module"

[pavoljuhas]

Description of the issue

Per internal proto checker, field name module introduced in #6212 is discouraged, because it overlaps with C++ keyword module.
Please rename to, e.g., gate_module.

Cirq version

1.5.0.dev at 2bbc3c4

[pavoljuhas]

cc @mhucka