[lworld] RFR: 8254326: [lworld] [lw3] Extend definition of empty inline types

[Frederic Parain]

Please review these changes which extend the runtime definition of empty inline types to also include inline type with
only empty non-static fields.

This is a first step of an attempt to unify the definition of empty inline types between the runtime and the JITs.

Thank you,

Fred

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Commit messages:
 - Adjust and comment with JIT code
 - Unify empty type definition

Changes: https://git.openjdk.java.net/valhalla/pull/220/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=220&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254326
  Stats: 34 lines in 3 files changed: 17 ins; 6 del; 11 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/220.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/220/head:pull/220

PR: https://git.openjdk.java.net/valhalla/pull/220