RFR: 8319747: galoisCounterMode_AESCrypt stack walking broken

[Daniel Jeliński]

This PR fixes stack walking by removing incorrect RBP change in the middle of a stub.

I also changed the register assignment to avoid saving RSI on Windows.

Testing:
- test/hotspot/jtreg/compiler/codegen/aes/TestAESMain.java still passes, both on Windows and Linux
- mach5 tier1-2 (including security and TLS-heavy networking tests) still pass
- the generated flamegraphs (attached in JBS) show the correct stack trace with this fix

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Commit messages:
 - Remove problematic rbp save, rename registers

Changes: https://git.openjdk.org/jdk/pull/16567/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16567&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319747
  Stats: 15 lines in 1 file changed: 0 ins; 9 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/16567.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16567/head:pull/16567

PR: https://git.openjdk.org/jdk/pull/16567