Use the project--list as history when prompting for a project

Use the project--list as history when prompting for a project

The project--list is already ordered such that the most recently used
projects are at the front.  Now we use it as the minibuffer history
when prompting for a project.

To avoid savehist from picking up project--list as a minibuffer
history variable and overriding our own persistence mechanism, we
don't pass project--list directly as a history variable, but instead
pass project--dir-history or project--name-history, dynamically-bound
to an appropriate value.  project--dir-history and
project--name-history won't be persisted since they're always unbound
at the top level; but if they are persisted anyway somehow, it won't
affect us.

If we later find a way to rely on savehist for persistence instead of
having our own mechanism, we can change the in-memory format of
project--list to be just a list of directories, and our explicit calls
to project--add-dir can be replaced by let-binding
history-delete-duplicates=t, history-length=t.

* lisp/progmodes/project.el (project--remember-dir): Add.
(project-remember-project): Use project--remember-dir.
(project--name-history, project-prompt-project-name)
(project--dir-history, project-prompt-project-dir): Pass a
preprocessed project--list as HIST to completing-read.  (bug#67310)
(project-switch-project): Call project--remember-dir.