Refactor testcase codes. It's repeated.

Refactor db:structure:load task.

Fix GH #4259. When we execute schema dumper, we must remove table_name_prefix and table_name_suffix.

Add prev_quarter and next_quarter methods in Time/Date/DateTime calculations.

Similar to prev_month and next_month, it returns the date with the same day
in the previous or next quarter:

    t = Time.local(2010, 5, 8) # => Sat, 08 May 2010
    t.prev_quarter             # => Mon, 08 Feb 2010
    t.next_quarter             # => Sun, 08 Aug 2010

Closes #6402

Prevent concurrent compilation of templates - closes #6400

Correct the AP test。

Closes #6007

Also use if/else block to not use short circuit return

add :nodoc: to AV StylesheetIncludeTag, JavascriptIncludeTag and 
AssetIncludeTag [ci skip]

Fix #5990

* remote:
  move fanout back to a global variable, add a mutex for safety

Refactor db:structure:dump task.

Remove extra test case.

Make the test description better reflect what is happening

Rename testcase name. It's wrong in the context.