cmdline: Enable plymouth splash and disable blinking cursor by default

3 jobs for splash in 4 minutes and 25 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #237312
librem5
builtin_tests

00:00:39

 
  Package
passed #237313
librem5:arm64
package:deb-debian-buster:arm64

00:02:00

 
  Test Package
passed #237314
librem5:arm64
lintian-debian-buster-package:arm64

00:01:45