Add Plymouth configuration setup

[ComicShrimp]

Add Plymouth boot splash support as opt-in in installation with the possibility to choose the theme (Only default plymouth themes available).

• This fix issue: Add support for Plymouth #1796

Tests and Checks

• I have tested the code!

[svartkanin]

Can you remove all the translation file changes from this PR otherwise it's massive.

Also this should not be a new root entry in the menu, we can probably fit this under Bootloader

[ComicShrimp]

Can you remove all the translation file changes from this PR otherwise it's massive.

Done, although the CI for translations will fail, but I can add it after the review no problem.

Also this should not be a new root entry in the menu, we can probably fit this under Bootloader

Sure, seems better to me, I'll make those changes and address the DISABLED entry.

[svartkanin]

I'll address the translation pipeline, the pipeline was recently added and shouldn't be failing on such PRs

[svartkanin]

#4576 should fix the broken check

[svartkanin]

@ComicShrimp could you rebase master the build should pass now

[ComicShrimp]

@svartkanin done. All checks pass now.