plugins/stoptrigger: TCG plugin to stop execution under conditions

plugins/stoptrigger: TCG plugin to stop execution under conditions

This new plugin allows to stop emulation using conditions on the
emulation state. By setting this plugin arguments, it is possible
to set an instruction count limit and/or trigger address(es) to stop at.
The code returned at emulation exit can be customized.

This plugin demonstrates how someone could stop QEMU execution.
It could be used for research purposes to launch some code and
deterministically stop it and understand where its execution flow went.

Co-authored-by: Alexandre Iooss <erdnaxe@crans.org>
Signed-off-by: Simon Hamelin <simon.hamelin@grenoble-inp.org>
Signed-off-by: Alexandre Iooss <erdnaxe@crans.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20240715081521.19122-2-simon.hamelin@grenoble-inp.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240718094523.1198645-5-alex.bennee@linaro.org>