RFR: 8317235: Remove Access API use in nmethod class

[Thomas Schatzl]

Hi all,

  please review this cleanup that removes use of the Access API (supposed to be used for Java heap access) for accessing some C heap values.

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - 8317235 initial version

Changes: https://git.openjdk.org/jdk/pull/15962/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15962&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317235
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15962.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15962/head:pull/15962

PR: https://git.openjdk.org/jdk/pull/15962