Support syncing a view with the value of an expression

[xusheng6]

People wish to be able to sync the hex/linear view with the value of a registry, commonly rsp or rbp. We can extend this to the value of any expressions since the value of a register can already be evaluated as an expression.

I am not sure the best route to implement this. Right now the debugger is using BN native views, and these do not have the ability to sync with a value. Subclassing these might be the best approach, but I am not sure how easy/difficult it is.