roll: pigweed pw_{async2,channel}: Split up docs

This change only splits existing content into separate docs.
It doesn't introduce new content, aside from minor
"glue content" that connects the docs together more
seamlessly.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/243877
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: 20f956e960d94a6584961924b5f7b73186a8e1c6

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: ce2aaba09bc030..20f956e960d94a
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8733348381407098737
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I060d98993a5740b8182385d8a1da53e389663ff3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/showcase/sense/+/243973
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
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 7e7a4e7..4cc86ed 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -49,8 +49,8 @@
     module_name = "pigweed",
     # ROLL: Warning: this entry is automatically updated.
     # ROLL: Last updated 2024-10-22.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8733351429390795105.
-    commit = "ce2aaba09bc030b828bb8036b229ed0317aba0e0",
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8733348381407098737.
+    commit = "20f956e960d94a6584961924b5f7b73186a8e1c6",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
 )
 
@@ -58,8 +58,8 @@
     module_name = "pw_toolchain",
     # ROLL: Warning: this entry is automatically updated.
     # ROLL: Last updated 2024-10-22.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8733351429390795105.
-    commit = "ce2aaba09bc030b828bb8036b229ed0317aba0e0",
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8733348381407098737.
+    commit = "20f956e960d94a6584961924b5f7b73186a8e1c6",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
     strip_prefix = "pw_toolchain_bazel",
 )