config/filesystem: fix and improve per-fs default mount options.
packages/fs: do not mess with journal_data on ext2.
packages/fs: do not enable swap at mount time.
config/filesystem, packages/fs: use discard selectively.
scripts/parser: finally fix escapes (\x2f etc.) in systemd-style arguments.
scripts/shell.utils: enclose stage name in ''-quotes as it is subject to eval.