Refactor Project API to reflect changes upstream

projectile-project-root no longer returns `default-directory` if not in
a project (it returns nil). As such, doom-project-* functions (and their
uses) have been refactored.

+ doom-project-p & doom-project-root are aliases for
  projectile-project-p & projectile-project-root.
+ doom-project-{p,root,name,expand} now has a DIR argument (for
  consistency, since projectile-project-name and
  projectile-project-expand do not).
+ The nocache parameter is no longer necessary, as projectile's caching
  behavior is now more sane.
+ Removed some projectile advice/hacks that are no longer necessary.
+ Updated unit tests

modules/completion/helm/autoload/helm.el

@@ -13,7 +13,7 @@
   (interactive)
   (call-interactively
    (if (or (file-equal-p default-directory "~")
-           (when-let* ((proot (doom-project-root 'nocache)))
+           (when-let* ((proot (doom-project-root)))
              (file-equal-p proot "~")))
        #'helm-find-files
      #'helm-projectile-find-file)))