perf(cpc): split disk-image-uefi out of disk-image series file

Due to how `disk-image` file is structured, it builds BIOS and UEFI
images at the same time. However, certain images (e.g., GCE images)
require only UEFI image to be built, BIOS image is being simply
discarded. This results in longer build times.

Splitting out `disk-image-uefi` would allow images to use it instead of
`disk-image` and thus avoid building unused BIOS images.

`disk-image` now depends on `disk-image-uefi` for backward
compatibility.

(cherry picked from commit b40ce74fd6)

live-build/ubuntu-cpc/hooks.d/base/series/disk-image

@@ -1,5 +1,5 @@
+depends disk-image-uefi
 base/disk-image.binary
-base/disk-image-uefi.binary
 base/disk-image-ppc64el.binary
 provides livecd.ubuntu-cpc.ext4
 provides livecd.ubuntu-cpc.initrd-generic

live-build/ubuntu-cpc/hooks.d/base/series/disk-image-uefi

@@ -0,0 +1,8 @@
+base/disk-image-uefi.binary
+provides livecd.ubuntu-cpc.ext4
+provides livecd.ubuntu-cpc.initrd-generic
+provides livecd.ubuntu-cpc.initrd-generic-lpae
+provides livecd.ubuntu-cpc.kernel-generic
+provides livecd.ubuntu-cpc.kernel-generic-lpae
+provides livecd.ubuntu-cpc.manifest
+provides livecd.ubuntu-cpc.filelist