Test for split edit file ordering using failover scenario

TestHLogMethods#testGetSplitEditFilesSorted tests the ordering of split edit files. However, we should have a test covering more realistic scenario.

Suppose there are two split edit files for one region.

Their edits are as the following

File 1:
edit id 1001
edit id 1002
edit id 1003

File 2:
edit id 2001
edit id 2002
edit id 2003

As the current logic, file 1 is named "1003" and file 2 is named "2003".

Suppose region's seq id is 1000 before replaying edits files.

So we will replay all the edits in File 1 and File 2

However, if we replay File 2 first, the following case could result in data loss:
1.Completing File 2 replay.
2.Do the internalFlushcache. See HRegion#replayRecoveredEdits:
if (flush) internalFlushcache(null, currentEditSeqId, status);
3.the regionserver crashes
4.Region is assigned to another server, and its seq ID becomes 2003
5.File1 will be skipped when replaying edits