bug#43153: Add new command project-find-dir (and move binding of project-dired)

[Juri Linkov]

> Here's a quick implementation of this feature inside project-dired:

Thanks, I tried it and everything's working as expected.

> Note that the user can simply press RET without typing any directory name
> and that will launch Dired in the project root.

This is a nice feature.

> That seems like it might make having a separate command unnecessary, since
> 'C-x p D' and 'C-x p d RET' take the same number of keypresses. The latter
> might make you move your hand farther, though.

We had such discussion about 'C-x v d' where the request
was for a command that doesn't require RET.  But 'C-x v D'
can't be used because it's bound to 'vc-root-diff'.

BTW, I have such customization:

  (define-key project-prefix-map "V" vc-prefix-map)

to allow vc commands in a project, e.g. 'C-x p V D' for 'vc-root-diff'.