Firefox 108 on POWER

Now that the Talos II is back in order and the Fedora 37 upgrade is largely behind me, it's now time to upgrade Firefox to version 108. There's some nice performance improvements here plus a hotkey for about:processes with Shift-Escape. Support for WebMIDI seems a little gratuitous, but what the hey (haven't tried it yet, the Macs mostly handle my music stuff), and there are also new CSS features. As before linking still requires Dan Horák's patch from bug 1775202 or the browser won't link on 64-bit Power ISA (alternatively put --disable-webrtc in your .mozconfig if you don't need WebRTC). Otherwise, we were able to eliminate one of our patches from the PGO-LTO diff, so use the new one for Firefox 108 and the .mozconfigs from Firefox 105.