bug#41821: 28.0.50; read-directory-name in vc commands should provide defaults from projects

[Juri Linkov]

> Apparently Juri wants to use certain data collected and saved by project.el
> UI, for convenience.

This feature was implemented to address Stephen's concerns in
https://debbugs.gnu.org/38044#233

> The alternative would be to introduce some separate history-keeping feature
> for the cases when VC code needs to ask the user to point to
> a VC repository.

It wouldn't be rational to duplicate this feature.
Rather I think the project-list should be updated
even on using vc commands such as 'C-x v d', i.e.
project and vc should be more tightly integrated.