Cache compressed /opt/asdf directory when building gemnasium-maven image

Problem to solve

It takes too much time to build the gemnasium-maven:3 image, the non-FIPS variant based on Debian. That's because /opt/asdf is compressed when building the image, and that directory contains many versions of Java, Maven, etc.

A workaround is to skip the gemnasium-maven child pipeline by putting [gemnasium only] or [gemnasium-python only] in the title of the MR, if this is an MR, but that's not always an option.

Proposal

Cache /opt/asdf.tar.zst using CI cache, and skip most of install.sh when retrieving it from the cache.