feature: expose the distribution type for use by features in choosing installation paths

[Common-utils has a bit of baseline distribution identification](https://github.com/devcontainers/features/blob/fbdc4556d519512736a8e2abfb3e03fcb2c9e0c7/src/common-utils/main.sh#L293) - enough to know what kind of package manger is in play, so that you can have a feature that doesn't just assume Debian and `apt-get` availability. Rather than making all feature developers replicate this bit of code, it would be hugely beneficial to drop it into a function and return a value so that `install.sh` scripts could use that information to know how to proceed with various distributions, or even to report that other distributions just "aren't supported" for that feature.

(related to https://github.com/orgs/devcontainers/discussions/33)