main/postmarketos-base: stop the power key from shutting down devices (MR 1499)

Pressing power button should not power off a device. Although it is
expected on desktops and laptops, it isn't expected on phones and
tablets. Instead it should just turn off the screen or go into a deep
sleep, but that isn't handled by elogind. So let elogind just ignore the
button altogether.

Also re-order the dependencies alphabetically while we're touching the
package anyway