Changes for Horizon and live CD environments

Changed easy-kernel config on ppc: These eval boards set config options that cause pata-macio to panic on Power Macintosh systems. Right now, the Power Mac is a significantly more important target for us. The eval board support was new for 5.15 anyway, which hasn't been shipped to any users yet.

Changed easy-kernel config on ppc64: More network drivers as requested by @djt.

An adelie-fonts package was added, and each desktop env pulls it in, so that missing fonts don't make for a weird experience.

Mesa was updated to 21.3.9 (from 21.3.8), and an upstream not-yet-released patch was pulled in to fix operations on Nouveau, allowing Adélie graphical environments to work on iMac G4.

dnsmasq was packaged for network boot testing.

Many fixes were added for livecd-support, documented in its commit message.

Horizon was updated to 0.9.8_pre7, bringing a multitude of fixes.