Task AB# 1310793: [LevelDB] Allow per-platform log buffer size

[yabmek-msft]

https://dev-mc.visualstudio.com/Minecraft/_workitems/edit/1310793

First commit moved over ability to log buffer size on a per platform basis based on https://github.com/Mojang/leveldb-mcpe/commit/6d245c4cc2022b503e68579fd6994d6e198e6cda. Some adjustment were made to this cherry-picked commit because of changes made to the upstream:

• Windows and posix platforms now use port_stdcxx.h instead of port_win.h and port_posix.h respectively, so the changes to those two files was consolidated into port_stdcxx.h

Second commit fixed log tests.