roll: pigweed pw_rpc: Add callback writes to raw RPC call objects

This adds a new API to pw_rpc's RawServerReaderWriter and
RawClientReaderWriter which allows users to directly serialize their
RPC payloads to the RPC system's encoding buffer instead of a requiring
a copy from an externally-managed buffer.

This type of direct encoding buffer access is already possible through
the pwpb and nanopb RPC APIs through the use of callback members in
their generated structs. Enabling it in raw_rpc provides better parity
with these other protobuf libraries.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/239353
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: 8e2fc6cfe825631416043a972cdd93875562a4fd

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 02a68bb680ebdd..8e2fc6cfe82563
Roller-URL: https://ci.chromium.org/b/8735072212683658017
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I812b49ab2c74d59b0eb3b36bb94c2ad20b5974a1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/bazel/+/239872
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/MODULE.bazel b/MODULE.bazel
index c548493..b68da83 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -49,8 +49,8 @@
     module_name = "pigweed",
     # ROLL: Warning: this entry is automatically updated.
     # ROLL: Last updated 2024-10-03.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8735080469787080225.
-    commit = "02a68bb680ebddeba8f0ad6cbbc6bb81d7568759",
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8735072212683658017.
+    commit = "8e2fc6cfe825631416043a972cdd93875562a4fd",
     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 2024-10-03.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8735080469787080225.
-    commit = "02a68bb680ebddeba8f0ad6cbbc6bb81d7568759",
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8735072212683658017.
+    commit = "8e2fc6cfe825631416043a972cdd93875562a4fd",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
     strip_prefix = "pw_toolchain_bazel",
 )