[lworld] RFR: 8359370: [lworld] allow instance fields of identity classes to be readable in the prologue phase

[Vicente Romero]

Before this fix only strict fields were readable in the prologue phase. The proposed fix should allow any instance fields of identity classes to be readable in the prologue phase,

TIA

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Commit messages:
 - updating tests
 - Merge branch 'JDK-8359370' of https://github.com/vicente-romero-oracle/valhalla into JDK-8359370
 - more simplifications
 - more simplifications
 - refact
 - refacts
 - more refactorings
 - more cleanups
 - adding some documentation
 - additional cleanups
 - ... and 5 more: https://git.openjdk.org/valhalla/compare/658a8d28...83b92556

Changes: https://git.openjdk.org/valhalla/pull/1490/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1490&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359370
  Stats: 457 lines in 20 files changed: 264 ins; 79 del; 114 mod
  Patch: https://git.openjdk.org/valhalla/pull/1490.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1490/head:pull/1490

PR: https://git.openjdk.org/valhalla/pull/1490