[roll pigweed] pw_web: Expose message descriptors and RPC method descriptors

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/107342

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: 29ac193641a6b62..a7a9307ba024188
Roller-URL: https://ci.chromium.org/b/8805367838982622241
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ib1414c6076cda7bee53a738b9b6fe3068b2a768b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/107653
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pigweed b/pigweed
index 29ac193..a7a9307 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit 29ac193641a6b62564faed097e6a8cce4f1b33b8
+Subproject commit a7a9307ba024188521c773b2cdca88bde4c874ab