Optimize edit handling in VisibleRefFilter

Checking each ref through the RefNames.isRefsEditOf is still several
percent of the total garbage created by a busy Gerrit server filtering
references for clients... most of which don't have pending edits.

Rewrite this handling to reduce the StringBuilder allocations so that
the user prefix is built once and reused over the refs.

Fix the TODO about filtering edits to visible changes; we have the
Set<Change.Id> readily available and can parse the Change.Id out of
the edit ref name to test in the set once we know the ref is owned by
the current user.

Rework much of the VisibleRefFilter logic to simplify the
!showMetadata case to short-circuit through the loop more quickly.
This speeds up advertisment generation for pushes by a very small
amount, but also simplifies every single branch so its worth the code
churn either way.

Change-Id: I15d97ec7783e8bd6c7a042a020cdcf4352273cab

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/RefNames.java

@@ -164,29 +164,17 @@ public class RefNames {
    * @return reference prefix for this change edit
    */
   public static String refsEditPrefix(Account.Id accountId, Change.Id changeId) {
-    return new StringBuilder(refsUsers(accountId))
-      .append('/')
-      .append(EDIT_PREFIX)
-      .append(changeId.get())
-      .append('/')
-      .toString();
+    return refsEditPrefix(accountId) + changeId.get() + '/';
+  }
+
+  public static String refsEditPrefix(Account.Id accountId) {
+    return refsUsers(accountId) + '/' + EDIT_PREFIX;
   }
 
   public static boolean isRefsEdit(String ref) {
     return ref.startsWith(REFS_USERS) && ref.contains(EDIT_PREFIX);
   }
 
-  public static boolean isRefsEditOf(String ref, Account.Id accountId) {
-    if (accountId == null) {
-      return false;
-    }
-    String prefix = new StringBuilder(refsUsers(accountId))
-        .append('/')
-        .append(EDIT_PREFIX)
-        .toString();
-    return ref.startsWith(prefix);
-  }
-
   static Integer parseShardedRefPart(String name) {
     if (name == null) {
       return null;