roll: pigweed pw_containers: Multiple container example

It is possible to add intrusive items to multiple containers, but only
if those containers have disjoint value_types. This isn't entirely
intuitive, so this CL adds examples, unit tests, and docs to make it
easier.

Additionally, in order facilitate the aforementioned unit tests, the
base type for map items has been unified into `pw::IntrusiveMapItem`,
and the intrusive item type used by `CheckItemType` has been renamed
to `pw::containers::internal::IntrusiveItem`.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/237472
Original-Revision: 819dd2ceb430eae53909bea7d5a23c7743ef0fc2

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: cfa4da0ff6f50b..819dd2ceb430ea
Roller-URL: https://ci.chromium.org/b/8735781600191061009
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id7444f4e47a64b6c36f84bdb0cc6c41660ddaf2a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/showcase/sense/+/238016
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/MODULE.bazel b/MODULE.bazel
index 34c04da..419b911 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -50,8 +50,8 @@
     module_name = "pigweed",
     # ROLL: Warning: this entry is automatically updated.
     # ROLL: Last updated 2024-09-25.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8735783421074670001.
-    commit = "cfa4da0ff6f50b81e21c3343312e15caf41a2bdf",
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8735781600191061009.
+    commit = "819dd2ceb430eae53909bea7d5a23c7743ef0fc2",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
 )
 
@@ -59,8 +59,8 @@
     module_name = "pw_toolchain",
     # ROLL: Warning: this entry is automatically updated.
     # ROLL: Last updated 2024-09-25.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8735783421074670001.
-    commit = "cfa4da0ff6f50b81e21c3343312e15caf41a2bdf",
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8735781600191061009.
+    commit = "819dd2ceb430eae53909bea7d5a23c7743ef0fc2",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
     strip_prefix = "pw_toolchain_bazel",
 )