[lworld] RFR: 8373912: [lworld] Small cleanups to InlineKlass [v2]

[Stefan Karlsson]

> A few cleanups found while scanning over the InlineKlass files:
> 
> * Fix include list and forward declarations
> * Move non-trivial implementation out of .hpp
> * Remove copy-n-past functions from InstanceKlass
> * Remove redundant CDS function overrides
> * Deduplicate null marker address calculation
> * Deduplicate allocate_instance
> * Fix raw casts from oop 
> * Tweak comments

Stefan Karlsson has updated the pull request incrementally with one additional commit since the last revision:

  Remove lingering references to InlineKlassFixedBlock

-------------

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1818/files
  - new: https://git.openjdk.org/valhalla/pull/1818/files/8cae412a..9b8c2816

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1818&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1818&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1818.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1818/head:pull/1818

PR: https://git.openjdk.org/valhalla/pull/1818