doc: Change distro installation documentation to be more consistent

The installation instructions for Debian and OpenSUSE have different
philosophies: Debian has screenshots for workarounds and OpenSUSE for
every user interaction.

Both sets of installation instructions now describe deviations from the
standard installation procedure and provide screenshots for more
complex steps. Links to their installation instructions have been moved
into each distro's respective section.

A new screenshot shows the console output following the instructions
after the grub failure in the debian installation section. To
maintain consistency in timestamps on the screenshots, new ones
replace their previous versions.

Remove png files which are no longer referenced in reproduce.rst.

Signed-off-by: Isaac Perry <isaac.perry@arm.com>