[roll third_party/pigweed] pw_protobuf: Make maximum varint size configurable

This adds a configuration option to set the number of bytes reserved for
nested message size varints when encoding a protobuf. A simple mapping
of varint size -> integer type is temporarily added to support the
stack-based encoder.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/39582

third_party/pigweed Rolled-Commits: 72b4313419452f5..f9ae189221f6860
Roller-URL: https://ci.chromium.org/b/8850745223304824176
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8850745223304824176
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I27f3ffe5b00384834addbd71e21ae9df9113be33
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/39981
Reviewed-by: 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 72b4313..f9ae189 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 72b4313419452f576ff3705040188e5ea75f01e7
+Subproject commit f9ae189221f68600468ee77761a89e0e2c16d010