Reimplement master local region initialization to better work with SFT

It is not like a normal region where we have a TableDescriptor so it can store the SFT implementation of its own. In the current implementation, if we change the global SFT configuration, the SFT implementation of the master local reigon will be changed and cause data loss.

First I think we could hard coded it to use DefaultSFT. The region is small and will not cause too much performance impact. Then we could find a way to manage the SFT implementation of it.

====== Update ======

The initialization of master local region depends on renaming, which can not work well on OSS. So we should also change it. The basic idea is to touch a '.initialized' file to indicate it is initialized. Need to consider how to migrate from the existing master local region where it does not have this file.

And we could also store the TableDescriptor on file system, so we can determine whether this is a SFT change. If so, we should do the migration before actually opening the master local region.