gdbstub: Move GdbCmdParseEntry into a new header file

gdbstub: Move GdbCmdParseEntry into a new header file

Move GdbCmdParseEntry and its associated types into a separate header
file to allow the use of GdbCmdParseEntry and other gdbstub command
functions outside of gdbstub.c.

Since GdbCmdParseEntry and get_param are now public, kdoc
GdbCmdParseEntry and rename get_param to gdb_get_cmd_param.

This commit also makes gdb_put_packet public since is used in gdbstub
command handling.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240628050850.536447-3-gustavo.romero@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240705084047.857176-32-alex.bennee@linaro.org>