[foreign-jextract] Integrated: 8253102: jextract should emit address to segment utility method on struct classes

[Athijegannathan Sundararajan]

added utility method to struct classes.

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Commit messages:
 - 8253102: jextract should emit address to segment utility method on struct classes

Changes: https://git.openjdk.java.net/panama-foreign/pull/324/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=324&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253102
  Stats: 141 lines in 4 files changed: 141 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/324.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/324/head:pull/324

PR: https://git.openjdk.java.net/panama-foreign/pull/324