Modernize equality operators in //ui

This CL is pure clean-up and contains no functionality changes.
Depending on the files covered in the CL (since the CL was generated
using git cl split), it does a subset of the following:
the following:
- Remove unneeded operator!= declarations/definitions since C++20 can
  automatically derive those from operator==.
- Default operator== where this is equivalent to the current behavior.
- Default operator<=> where this is equivalent to the current
  behavior.

This CL was uploaded by git cl split.

R=kylixrd@chromium.org

Bug: 40256175
Change-Id: I9d1c9cb13159aabb003358031fb9d8f88de533a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6532331
Auto-Submit: Jan Keitel <jkeitel@google.com>
Reviewed-by: Elly FJ <ellyjones@chromium.org>
Commit-Queue: Jan Keitel <jkeitel@google.com>
Cr-Commit-Position: refs/heads/main@{#1464586}

ui/views/controls/table/table_grouper.h

@@ -13,11 +13,7 @@ struct VIEWS_EXPORT GroupRange {
   size_t start;
   size_t length;
 
-  bool operator==(const GroupRange& other) const {
-    return start == other.start && length == other.length;
-  }
-
-  bool operator!=(const GroupRange& other) const { return !(*this == other); }
+  friend bool operator==(const GroupRange&, const GroupRange&) = default;
 };
 
 // TableGrouper is used by TableView to group a set of rows and treat them