Blender Git Loki

Add `--open-last` CLI argument that opens the most recent file

Add a CLI argument `--open-last` that opens the most recent file,
effectively doing the same as {key Ctrl Shift O}, {key Enter} after
starting Blender.

When there are no known recent files, print a warning and do nothing,
showing the startup file instead.

Note that this does not try to be smart about restoring the last Blender
session. It just opens the file from disk, as if the user had typed
`blender $(head -n1 ~/.config/blender/2.93/config/recent-files.txt)`.

There is also no smartness when that file cannot be opened; it behaves
exactly the same as typing the most recent filename on the CLI.

Reviewed by: mont29, campbellbarton

Differential Revision: https://developer.blender.org/D10563