Revert "systemd: Fix timeouts mounting swap partitions and other devices"

This reverts commit 3e2f0a3405d13421acd9780f1a1d3678d0a672bb.

Instead, it uses systemd's conf.d/ feature to achieve this, rather than having to carry a bunch of gnarly patches.

Uses 30s for start timeouts and 10s for stop timeouts.

Also changes to use a compile-time default of 30s in timeouts (instead of the default of 5s).

Signed-off-by: Rune Morling <ermo@serpentos.com>

Checked that the timeout values are set in /usr/lib/systemd/system.conf.d/ and /usr/lib/systemd/user.conf.d/ vendor dirs.