Add Lock editing for custom properties to prevent keying.

Basically the idea came after me finding out that the "Whole Character/Selected Bones" keying sets don't key/add unwanted keys to the locked channels which now became my default option and I know many people don't know about this not a youtube tutorial i checked or even the manual has mentioned this important aspect, However this doesn't apply to the custom properties.

I know the lock is meant for the transform channels but I think it should be added to the custom properties maybe with a different purpose/icon to indicate that it's meant to prevent "Whole Character/Selected Bones" from keying.