[roll third_party/pigweed] pw_stream: Add Rust streaming interfaces

These interfaces mirror the functionality of Rust's `std:io`.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/152070

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9e1ec307891de20..698999aa748cb6d
Roller-URL: https://ci.chromium.org/b/8777557323375551393
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia74e1eb7c585be119fc246a350a1da45b0b2018d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/152874
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 9e1ec30..698999a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9e1ec307891de20eddfa67a4107467a6bf8ce608
+Subproject commit 698999aa748cb6d128070de367690fdaa1dcd697