tests/plugins/insn: made arg inline not positional and parse it as bool

tests/plugins/insn: made arg inline not positional and parse it as bool

Made argument "inline" not positional, this has two benefits. First is
that we adhere to how QEMU passes args generally, by taking the last
value of an argument and drop the others. And the second is that this
sets up a framework for potentially adding new args easily.

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210730135817.17816-11-ma.mandourr@gmail.com>
[AJB: fix check-tcg tests calling arg=inline]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>