gallium/tools: improve option handling in dump_state.py

gallium/tools: improve option handling in dump_state.py

Previously we inherited some options from parse.py, but
that made no sense for some of the options that are not
needed for dump_state.py (such as --plain, as we output
only JSON format text.)

So, remove the inherit and implement filename argument
here independantly.

Signed-off-by: Matti Hamalainen <ccr@tnsp.org>
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10648>