[lworld] RFR: 8366794: [lworld] "assert(!is_null(v)) failed: narrow klass value can never be zero" with -Xint and COH

[Coleen Phillimore]

The oop_size() function can't get the Klass from the oop with UseCompactObjectHeaders because there's some GC code that moves the klass out of the markWord somewhere.  Pass layout_helper() from the already fetched klass instead and disable the assert, like objArrayKlass::oop_size.
Testing with tier1-4 in progress.

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

Commit messages:
 - 8366794: [lworld] "assert(!is_null(v)) failed: narrow klass value can never be zero" with -Xint and COH

Changes: https://git.openjdk.org/valhalla/pull/1557/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1557&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366794
  Stats: 10 lines in 4 files changed: 4 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/valhalla/pull/1557.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1557/head:pull/1557

PR: https://git.openjdk.org/valhalla/pull/1557