Linux installers should install manpages to correct location

[NikolaMilosavljevic]

This isn't working today due to a bug infra that tries to collect manpages from https://github.com/dotnet/sdk/tree/main/documentation/manpages. There are two issues with this: 1) the folder contains more than manpages, i.e. there are tooling that we do not want to package/install, and 2) directory is referenced with incorrect casing and no manpages are found during build.

We are moving to a new model of building DEB and RPM packages, using common Arcade infra, see #43688

This new model requires Manpage items to be set, in the installer project. However new Arcade infra installs those to /usr/share/doc, which is not a correct location. It appears that there are several ways to package and install manpages, and they should most likely be installed ot /usr/share/man. This is still TBD.

Related Arcade issue: dotnet/arcade#15243