[roll third_party/pigweed] pw_stream: Rework the stream classes

- Derive all stream classes from a common base Stream class.
- Introduce Seek() and Tell() methods.
- Implement helper functions for seeking in pw_stream/seek.h.
- Expand the pw_stream documentation.
- Update existing Stream classes.

Original-Requires: pigweed-internal:14760
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/56820

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: ef588a3530629e7..7b62e93287f40f8
Roller-URL: https://ci.chromium.org/b/8838443550904915104
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8838443550904915104
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I68f3a05d18253dda703f5fe5f5680c2014a84fd4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/57741
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 ef588a3..7b62e93 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit ef588a3530629e7717cdd28ff2cf6fc2e13eae30
+Subproject commit 7b62e93287f40f80a66b6866f3dca8d48fba2983