Debugger should make the creation of function at the current addrsss optional

[xusheng6]

When the target stops at an address and there is no function for it, the debugger will create a function at the address to allow the display of disassembly/ILs. This works well in most cases, however, when it comes to TTD backward debugging, stepping backwards in the code will create various function that only has one instructions in it, which severely limits the readability.

While a better approach for this would be to backward scan the execution trace to find the call/jmp instruction that leads to the function, but for now we might need a workaround for it.