Cache uncompressed data section as well

[jonjohnsonjr]

We spend ~half of our time decompressing the data section on rebuilds. This cuts that out when we have a cache hit, but this is also faster on a cache miss because we already have to decompress when we verify file checksums.

[jonjohnsonjr]

Measured go1.20 (unplugged, over wifi, YMMV):

Cold

Before

apko publish --arch amd64 --keyring-append  --repository-append     15.62s user 3.49s system 162% cpu 11.775 total

After

apko publish --arch amd64 --keyring-append  --repository-append     12.55s user 3.42s system 176% cpu 9.037 total

(11.775 -> 9.037 seconds)

Hot

Before

apko publish --arch amd64 --keyring-append  --repository-append     11.14s user 1.90s system 208% cpu 6.270 total

After

apko publish --arch amd64 --keyring-append  --repository-append     8.12s user 1.78s system 310% cpu 3.185 total

(6.270 -> 3.185 seconds)