roll: pigweed pw_containers: Add pw::EqualTo functor

This change introduces `pw::EqualTo`, a functor that performs quality
comparisons using `operator==`, similar to the C++14 `std::equal_to<>`
transparent operator functor.

Comprehesive unit tests and build system support for GN, Bazel, and
CMake are included.

Original-Bug: 464154008
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/353972
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Copybara-Verified: Copybara Prod <copybara-worker-blackhole@google.com>
Original-Revision: 7d509af2ea538defd42c0d92643b9652325e73ef

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: b766c313974805..7d509af2ea538d
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8695075063980689761
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ib0cf8d332803b4c32055a1b785b0762562079152
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/bazel/+/357532
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/MODULE.bazel b/MODULE.bazel
index f2bc52e..9f04c0f 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -42,7 +42,7 @@
     module_name = "pigweed",
     # ROLL: Warning: this entry is automatically updated by
     # ROLL: https://cr-buildbucket.appspot.com/builder/pigweed/quickstart.roll/pigweed-quickstart-bazel-roller
-    commit = "b766c313974805c3b239594fb0f94c0639bfb773",
+    commit = "7d509af2ea538defd42c0d92643b9652325e73ef",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
 )