RFR(S): 8165056: move JIT Compiler related files from runtime/ to compiler/ directory

[Liu Xin]

Hi, Reviewers,

Could you review this webrev?
https://cr.openjdk.java.net/~xliu/8165056/webrev/
JBS: https://bugs.openjdk.java.net/browse/JDK-8165056

The change is straightforward. Those 3 files below have been merged
into compilationPolicy.hpp/cpp.

simpleThresholdPolicy.cpp
simpleThresholdPolicy.hpp
simpleThresholdPolicy.inline.hpp

I ran hotspot/compiler tests and it's clear.

thanks,
--lx