[roll third_party/pigweed] pw_varint: Add missing includes

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98906

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 65b35f7d6df0859..ea5abc0a7c9cc89
Roller-URL: https://ci.chromium.org/b/8810725731936989697
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8810725731936989697
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iff7c0fd4800ec7f5e0308cddbfcbcdc5048d98c6
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/99100
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 65b35f7..ea5abc0 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 65b35f7d6df085918d47de7d49c1e5b0db70ec8f
+Subproject commit ea5abc0a7c9cc89796385e0eb7f472e30cb62d2e