Automate generation of Mock classes from Interface classes

[rfairley]

Describe the feature
Provide an automated way to write the declarations for a class like MockOsInterface from OsInterface. I.e., translate a virtual Interface function definition into a gmock Mock class function definition.

This involves writing out the googletest macros like:

OsInterface.h

    virtual int32_t OS_osSemaphoreWait (
        osSemaphoreId semaphore_id,
        uint32_t millisec
    ) const = 0;

↓

MockOsInterface.h

    MOCK_CONST_METHOD2(
        OS_osSemaphoreWait,
        int32_t(
            osSemaphoreId,
            uint32_t millisec
        )
    );

Reason for request
Similar to #183, this is to save time writing out the googletest declarations manually when it is a mostly mechanical process.

Timeline
No timeline - not urgent.

Additional information
googletest/googlemock is a popular framework, so there may already be tools that can do this in a generalized way. We should see what existing tools there are before writing our own.