CodeHealth: Remove use of DictionaryValue::Set in c/b/ash and ash/

This change removes the use of DictionaryValue::Set and replaces with
Value::SetKey() or Value::SetPath().

Bug: 1187023
Change-Id: I1b576a35ea0c604cf472c71ae19e457c0581feeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2968803
Auto-Submit: Fangzhen Song <songfangzhen@bytedance.com>
Commit-Queue: Fangzhen Song <songfangzhen@bytedance.com>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#895459}