Support setting the program entry point when the user is using the debugger without a binary view

[xusheng6]

Now that we can already use the debugger without a binary view, we lack the ability to add the breakpoint at the program entry point. This is of course reasonable since we originally rely on the information in the binary view set that breakpoint. Now that the info is gone, we cannot set it in the old way.

That said, we still have the path for the executable, and we can do a quick parse of the file and get its entry point, then apply the entry breakpoint accordingly. This is similar to something like this:

hex(BinaryViewType["Mach-O"].parse(raw_view).start)

Relevant to https://github.com/Vector35/debugger/issues/206