main/postmarketos-bootsplash: kill pbsplash before display-manager

If pbsplash is running when a display manager starts it often causes issues as display managers want to run on a particular VT, but are unable to switch the active VT since pbsplash has exclusive control of the framebuffer.

This was not an issue with tinydm as it has "needs local" in its service depends, avoiding the conflict. not sure why my tinydm initd has this, i guess tinydm wasn't affected due to how it and Phosh interact with the display.

Making other DMs not start until after local would solve the issue but it would also needlessly delay the boot process.

Until we have a better way to detect display managers starting and react to it, this will at least get devices working again. Though due to how openrc resolves service start order it may mean the splash is killed earlier than necessary.

Lets also revert !3887 (merged) as it isn't necessary anymore and breaks some usecases

Replaces !3890 (closed)

Fixes #1960 (closed)

/cc @Newbyte @craftyguy