Update installed Alpine packages

[jnoordsij]

Based on my analysis on composer installation requirements (see also composer/composer#12278), I spotted that the Alpine packages installed in this images could be improved in two ways:

• Replace p7zip with 7zip to follow upstream changes; see https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/46038/diffs
• Install 7zip and mercurial on all architectures; from https://pkgs.alpinelinux.org/packages?name=mercurial&branch=v3.21&repo=&arch=&origin=&flagged=&maintainer= and https://pkgs.alpinelinux.org/packages?name=7zip&branch=v3.21&repo=&arch=&origin=&flagged=&maintainer= it seems they should be available on all relevant architectures.

[alcohol]

Thanks