gdbstub: Implement qGDBServerVersion packet

gdbstub: Implement qGDBServerVersion packet

This commit adds support for the `qGDBServerVersion` packet to the qemu
gdbstub  which could be used by clients to detect the QEMU version
(and, e.g., use a workaround for known bugs).

This packet is not documented/standarized by GDB but it was implemented
by LLDB gdbstub [0] and is helpful for projects like Pwndbg [1].

This has been implemented by Patryk, who I included in Co-authored-by
and who asked me to send the patch.

[0] https://lldb.llvm.org/resources/lldbgdbremote.html#qgdbserverversion
[1] https://github.com/pwndbg/pwndbg/issues/2648

Co-authored-by: Patryk 'patryk4815' Sondej <patryk.sondej@gmail.com>
Signed-off-by: Dominik 'Disconnect3d' Czarnota <dominik.b.czarnota@gmail.com>
Message-Id: <20250403191340.53343-1-dominik.b.czarnota@gmail.com>
[AJB: fix include, checkpatch linewrap]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250603110204.838117-17-alex.bennee@linaro.org>