meson: adds post meson setup/--reconfigure summary for auto features

As suggested by @gkiagia , adds calls to summary() function for each feature that is by default set to auto, so that an overview of their effective state is printed at the end of meson setup or meson --reconfigure command.

Currently ordering is a bit messy but tidying it up would detach the summary() functions from the dependencies they rely on and could be done later along with meson_options.txt re-ordering so that the two match as much as possible.

Assuming I didn't miss anything, the only one missing is the summary for 'v4l2' for which I could not find anything that's actually testing for it, hence its state is whatever it's set to.