Make symbol.get bulletproof against duplicated symbols

[disconnect3d]

@lebr0nli pointed out an interesting case with symbol.get failing when Pwntools+Pwndbg is used: #1605 (comment)

The bug actually does not require Pwntools at all and was partially caused by our _add_main_to_symbols hook. I am going to remove that hook in #1609 if tests passes, since it seems reduntant.

However, that does not really fix the problem as there may always be duplicated symbols such that info symbols main would show:

pwndbg> info symbol main
main in section .text of /pwndbg/bug/vaccine
main in section .text of /pwndbg/bug/vaccine

This can probably be mitigated by doing something like:

loc_string, *_ = result.split(...)

instead of:

loc_string, _ = result.split(...)

In the symbol.get implementation.

This would also mean we would effectively always assume the first symbol is the one we want to use, but I also do not see a good other way to resolve the duplicated symbol issue.