[jdk16u] RFR: 8256215: Shenandoah: re-organize saving/restoring machine state in assembler code

[Aleksey Shipilev]

This unbreaks x86_32 tests with Shenandoah.

Additional testing:
 - [x] Linux x86_64 fastdebug tier1,2
 - [x] Linux x86_32 fastdebug tier1,2 `-XX:+UseShenandoahGC -XX:+UseSSE=1`
 - [x] Linux x86_32 fastdebug tier1,2 `-XX:+UseShenandoahGC -XX:+UseSSE=2`

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Commit messages:
 - Backport a97aedff9f622ba6816b7550588f1d429bff2483

Changes: https://git.openjdk.java.net/jdk16u/pull/69/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=69&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256215
  Stats: 118 lines in 2 files changed: 69 ins; 13 del; 36 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/69.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/69/head:pull/69

PR: https://git.openjdk.java.net/jdk16u/pull/69