[roll third_party/pigweed] pw_rpc: Expose Request/Response from MethodInfo

pw::rpc::internal::MethodInfo Request and Response types are handy when
building helpers for rpc calls, but they are not available for
downstream projects. While other parts of MethodInfo could be too much
of the information for downstream projects and shouldn't be exposed -
these two types are straightforward enough to be exposed.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/97906

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 803298e1237eb56..55b450bcdc4eead
Roller-URL: https://ci.chromium.org/b/8811259378620751217
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8811259378620751217
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I72c39e1bc41c5fd6b6d8acd2e942aabe17ba56c7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/98228
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/third_party/pigweed b/third_party/pigweed
index 803298e..55b450b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 803298e1237eb56ea96d1c7b69b093d0d553f1bc
+Subproject commit 55b450bcdc4eead4bbe7178e7c2e3d08a79d5afa