RFR: Loom cleanups

[Stefan Karlsson]

Various cleanups and restructuring.

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Commit messages:
 - Restructure stackChunkOop bitmap
 - Move copy_alignment to continuation.cpp
 - Restructuring stackChunkOop files
 - Small cleanups to instanceStackChunkKlass.cpp
 - Cleanup InstanceStackChunkKlass friendship
 - Limit classes using chunk_frames
 - Split out classes out of InstanceStackChunkKlass files
 - Simplify InstanceStackChunkKlass copy
 - Move inlined functions
 - Simpler devirtualization of bitmap closure
 - ... and 1 more: https://git.openjdk.java.net/loom/compare/d405b732...7ab30096

Changes: https://git.openjdk.java.net/loom/pull/108/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=108&range=00
  Stats: 4001 lines in 50 files changed: 2285 ins; 1617 del; 99 mod
  Patch: https://git.openjdk.java.net/loom/pull/108.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/108/head:pull/108

PR: https://git.openjdk.java.net/loom/pull/108