[lworld] RFR: 8268021: [lworld] [AArch64] fix support for InlineTypeReturnedAsFields

[Nick Gasson]

The code to support this on AArch64 was already mostly written but
untested or bit-rotted. This patch also contains the allocation
optimisation to MacroAssembler::store_inline_type_fields_to_buf() from
JDK-8263067.

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Commit messages:
 - 8268021: [lworld] [AArch64] fix support for InlineTypeReturnedAsFields

Changes: https://git.openjdk.java.net/valhalla/pull/461/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=461&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268021
  Stats: 260 lines in 8 files changed: 88 ins; 86 del; 86 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/461.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/461/head:pull/461

PR: https://git.openjdk.java.net/valhalla/pull/461