[roll third_party/pigweed] pw_rpc: Get a MethodClient from a Method instance

- Allow getting a MethodClient from a Method instance, rather than using
  the name or the ID, which is internal.
- Temporarily expose the ID overload of method() so that users can
  migrate to the new API.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/97680

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: c294be0b0ac9f3d..e29b5fd0be53cb0
Roller-URL: https://ci.chromium.org/b/8811789391550053153
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8811789391550053153
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie000a0a28fd412c61696deb339475ee451287fd1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/97675
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 c294be0..e29b5fd 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit c294be0b0ac9f3dde0aaeec38436acead10d4f52
+Subproject commit e29b5fd0be53cb0b01859ca5970874704a830675