[base] Replace GetList().{emplace,push}_back with Append

This change replaces usages of base::Value::GetList() followed by either
emplace_back() or push_back() with base::Value::Append(). This is
because of the upcoming change to GetList() to return a base::span
instead, which does not support either emplace_back() or push_back().

This is a mostly mechanical change. Steps to reproduce:
- sed -i 's/GetList().push_back/Append/g'
- sed -i 's/GetList().emplace_back/Append/g'
- git cl format
- Manually fixing the breakage in base/json/json_writer_unittest.cc
  and tools/json_schema_compiler/util.cc

TBR=afakhry,boliu,eugenebut,mmoroz,rdevlin.cronin,[email protected],sandersd

Bug: 646113
Change-Id: I2f13fd0efa7fe712f7659500404192be4a344e14
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1796427
Commit-Queue: Jan Wilken Dörrie <[email protected]>
Reviewed-by: Dan Sanders <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Cr-Commit-Position: refs/heads/master@{#695711}
diff --git a/extensions/browser/computed_hashes.cc b/extensions/browser/computed_hashes.cc
index 263eaa6..1533306b 100644
--- a/extensions/browser/computed_hashes.cc
+++ b/extensions/browser/computed_hashes.cc
@@ -159,7 +159,7 @@
   for (const auto& hash : hashes) {
     std::string encoded;
     base::Base64Encode(hash, &encoded);
-    block_hashes->GetList().emplace_back(std::move(encoded));
+    block_hashes->Append(std::move(encoded));
   }
 
   auto dict = std::make_unique<base::DictionaryValue>();