tests/plugins/mem: introduce "track" arg and make args not positional

tests/plugins/mem: introduce "track" arg and make args not positional

This commit makes the plugin adhere to the new plugins arg-passing
scheme by expecting full-form boolean args instead of short-form
booleans. This necessitates that we introduce a new argument, here
"track", to accept "r", "w", or "rw".

Also, it makes arguments not positional and we only care about the last
value specified for a certain argument.

callback/inline args are now supplied separately as bool arguments so
that both can be enabled individually.

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210730135817.17816-12-ma.mandourr@gmail.com>