Better naming of the cache directory

[mikhailnov]

This is microdnf, not yum. Normal dnf uses /var/cache/dnf. It is not a good idea to reuse it. But there is no need to use /var/cache/yum, at least in ROSA where this package did not exist before.

Naming cache directory as "microdnf" allows to own it properly in the RPM package.

[ this pull request is a suggestion, I am not sure that you will want to change location on the fly, breaking compatibility ]

[Conan-Kudo]

I'm not sure we wouldn't want to use the /var/cache/dnf directory. @kontura, what do you think?

[mikhailnov]

Are any locks made to prevent parallel usage of it by dnf and microdnf?