gdb/testsuite: make gdb_breakpoint, runto and runto_main use parse_args

In preparation to adding an option with argument to runto, change these
procs to use parse_args to manage their args (variable arguments).
These three procs have to be converted at the same time, because they
pass args to each other.

I would have like to allow passing options mixed with non-option
arguments, to allow:

  gdb_breakpoint -qualified the_function

But that would be a larger and more difficult change, so we'll have to
stick having options after, like this:

  gdb_breakpoint the_function -qualified

Change all callers that do use options to add the leading dash.

This patch removes the "last one wins" aspect of the message/no-message
options in gdb_breakpoint and runto, but I don't think it's important.
I don't think there is actually a spot that passes both.  I added some
checks in those procs to ensure that.

Change-Id: I1500c60c4b1705ad5cd982d9324b627900ce411b
Reviewed-By: Tankut Baris Aktemur <TankutBaris.Aktemur@amd.com>