[roll third_party/pigweed] pw_transfer: Assume a minimum window size when reserving space

A pw_transfer receiver estimates how much data the sender can fit in a
chunk by trying to calculate the protobuf overhead of transfer metadata.
On the first chunk of a transfer, this calculation is performed before
a window size is set (as setting a window size requires a max chunk
size), potentially resulting in a larger initial chunk size.

This caused issues in the case of retries, as a retried chunk could
advertise a smaller (correct) window size than the initial chunk,
invalidating any in-flight data transmissions.

This updates the code to assume a minimum window size of one chunk when
making its initial overhead calculation.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/206890

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 2593707a02b0c21..87126e11b80d206
Roller-URL: https://ci.chromium.org/b/8749572311125196865
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7de13c21ba11b47e0c78ba14477b0f09d8cc44b5
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/206873
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 2593707..87126e1 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 2593707a02b0c211f21c738180dbd4439fa7013d
+Subproject commit 87126e11b80d206e9745b057f29ca23f6cd028c2