Rename //ui/base/{cursor:cursor_base => cursor}

The split between //ui/base/cursor and //ui/base/cursor:cursor_base was
artificially created to allow Blink to use cursor.h without depending on
other platform-specific code. Now, after https://crrev.com/c/3284990
where the //ui/base/cursor target was moved to //ui/aura/cursor,
//ui/base/cursor:cursor_base is the only target remaining in
ui/base/cursor/ and there's no need to name it differently than its
directory.

Additionally, this CL fixes some includes and dependencies on this
target.

Bug: 1270302
Change-Id: I384e177a915c0e9e036cf1c9a7f48f65d9f850af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3306587
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Ben Wells <benwells@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Henrique Ferreiro <hferreiro@igalia.com>
Cr-Commit-Position: refs/heads/main@{#948977}

diff --git a/ui/aura/BUILD.gn b/ui/aura/BUILD.gn
index 42d2606..d3f8da79 100644
--- a/ui/aura/BUILD.gn
+++ b/ui/aura/BUILD.gn

@@ -134,7 +134,7 @@
   ]
 
   public_deps = [
-    "//ui/base/cursor:cursor_base",
+    "//ui/base/cursor",
     "//ui/base/dragdrop:types",
     "//ui/base/dragdrop/mojom:mojom_headers",
     "//ui/base/ime",
@@ -226,7 +226,7 @@
     "//skia",
     "//testing/gtest",
     "//ui/base:test_support",
-    "//ui/base/cursor:cursor_base",
+    "//ui/base/cursor",
     "//ui/base/cursor/mojom:cursor_type",
     "//ui/base/ime/init",
     "//ui/compositor:test_support",