Investigate ExtendLockup hooks

[ValarDragon]

We need to look further into the hook calls for MsgLockupExtendDuration.

It currently calls OnTokensUnlocked and OnTokensLocked. I don't think this is right, it should instead get a new hook. This is because something like superfluid shouldn't think "start undoing superfluid lock" upon seeing the unlock hook for instance, its not the lock creator signalling intent to unwind. (In fact its the opposite!)

I suggest we make a new hook called OnLockExtended, and use that here.

Originally posted by @ValarDragon in #1253 (comment)