[lworld] RFR: 8370349: [lworld] Generalize some memory optimizations for strict final fields

[Quan Anh Mai]

Hi,

Some optimizations in `memnode.cpp` look at some properties of the pointer such as if it is a field of a value class, or if it is a field of a box class while the required assumption is that the pointer is to a strict final field. This PR cleans that up.

Please leave your reviews, thanks very much.

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Commit messages:
 - is_ptr_to_strict_final_field

Changes: https://git.openjdk.org/valhalla/pull/1692/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1692&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370349
  Stats: 41 lines in 3 files changed: 18 ins; 11 del; 12 mod
  Patch: https://git.openjdk.org/valhalla/pull/1692.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1692/head:pull/1692

PR: https://git.openjdk.org/valhalla/pull/1692