This PR cherry-picks the implementation for `base::HexEncodeLower` into our codebase, and converts all uses of the previous wallet implementation to use the base one. A follow-up PR will convert other places in the codebase where this base function will be appropriate. Bug: https://github.com/brave/brave-browser/issues/50911 Chromium changes: https://chromium.googlesource.com/chromium/src/+/0d2478d1df359731d1391637935e49f517e27bfe commit 0d2478d1df359731d1391637935e49f517e27bfe Author: David Benjamin <davidben@chromium.org> Date: Thu Oct 30 13:39:24 2025 -0700 Add base::HexEncodeLower and migrate a few callers Bug: 456472080 Change-Id: Ic3faa954edb6aec3f08675a02a55413b8a70e6b9 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7100923 Commit-Queue: David Benjamin <davidben@chromium.org> Owners-Override: Daniel Cheng <dcheng@chromium.org> Auto-Submit: David Benjamin <davidben@chromium.org> Reviewed-by: Daniel Cheng <dcheng@chromium.org> Cr-Commit-Position: refs/heads/main@{#1538143}