[SPLASH] Add PSplash and Plymouth support

Add splash-screen with both Plymouth and PSplash providers.

The providers are selectable from the configurator. If selecting Plymouth, the theme is also selectable from the configurator.

The default theme is CleaOS theme.

To improve Plymouth splash-screen behavior, it's started as soon as possible in the initramfs. The added tasks in the initramfs are executed only when selecting Plymouth. They are not active with PSplash.

JIRA Reference: [CLEAOS-614, CLEAOS-622, CLEAOS-623]

Tested on:

• QEMU arm
• Intel
• iMX by @davide.cardillo
• Raspberry Pi 5
• Raspberry Pi CM5 by @alessandro.pecugi

NOTE: on Plymouth the splash-screen is forced on no matter what bootloader argument are passed. TODO: let Plymouth fetch bootargs.

Signed-off-by: Nicola Sparnacci nicola.sparnacci@seco.com