feat(java): extract public Fury methods to BaseFury

[Munoon]

Extract public Fury method to the BaseFury interface and implement them in ThreadPoolFury and ThreadLocalFury, so end users can avoid using execute() and other utility methods.

Off topic: further steps might be changing BaseFury interface name to Fury while existing class renaming to something like FuryImpl. FuryBuilder should return the new Fury interface, so we will hide system methods like xwriteRef and others. WDYT?

[chaokunyang]

LGTM