Bring back the project--value-in-dir logic

Bring back the project--value-in-dir logic

Essentialy revert commit 2389158a31b4a12, restoring the changes
and fixing the conflicts.  Motivated by the problem brought up in
bug#59722 (behavior of project-find-files/regexp when switching
projects).  We should find other ways to improve performance.

* lisp/progmodes/project.el
(project--value-in-dir, project--vc-merge-submodules-p): Restore.
(project-try-vc, project-files, project--vc-list-files)
(project-ignores, project-buffers): Use.

* test/lisp/progmodes/project-tests.el
(project-vc-supports-project-in-different-dir): New test.

* test/lisp/progmodes/project-resources/.dir-locals.el:
* test/lisp/progmodes/project-resources/foo:
* test/lisp/progmodes/project-resources/etc: New files.