Make the `disassemble` and the `nearpc` commands have the same output style for the symbol names

The result of nearpc doesn’t respect set print asm-demangle on/off, so the symbol name it showed will not same as disassemble for some symbols. To change the result of nearpc showed, now we only can do set print demangle on/off because it affected the result of info symbol ... But there’s a problem. Since we cache the symbol name and only reset it when a new objfile is present, the old results we cached will make the output inconsistent. (I mean something like this will happen: