RFR (S) CR 8014878: Clean up class field layout code

[Aleksey Shipilev]

Hi,

This is the cleanup I promised to do for the CL code.

The first batch is here:
  http://cr.openjdk.java.net/~shade/8014878/webrev.01/

I would like to do this in incremental steps to ease the bisecting
should it bring any regressions. If you think something else needs the
refactoring, speak up, I'll add this to running tally of things to clean
up in the next patch.

Testing:
  - test/runtime/contended regression tests
  - full JPRT cycle vs hotspot-rt

Please review!

-Aleksey.