use gdb's `-list-feature` instead of heuristics

[cs01]

Is your feature request related to a problem? Please describe.
gdb features, such as whether reverse debugging is enabled, is currently guessed at by gdbgui.

Describe the solution you'd like
use -list-feature instead of guessing gdb's features

https://sourceware.org/gdb/onlinedocs/gdb/GDB_002fMI-Support-Commands.html#GDB_002fMI-Support-Commands