[lworld] RFR: 8271017: [lworld] Implement withfield changes from JDK-8269408 on AArch64

[Nick Gasson]

This just applies the changes in JDK-8269408 to the AArch64 port.

The old `InterpreterRuntime::withfield()` is removed as it has no more users, and I've renamed withfield2 to withfield (presumably this was the original intention?).

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Commit messages:
 - 8271017: [lworld] Implement withfield changes from JDK-8269408 on AArch64

Changes: https://git.openjdk.java.net/valhalla/pull/492/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=492&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271017
  Stats: 116 lines in 4 files changed: 5 ins; 105 del; 6 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/492.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/492/head:pull/492

PR: https://git.openjdk.java.net/valhalla/pull/492