[foreign-jextract] RFR: 8261498: jextract struct layout computer exceptions should include struct name for debugging

[Athijegannathan Sundararajan]

including struct name as part of exception message.

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Commit messages:
 - 8261498: jextract struct layout computer exceptions should include struct name for debugging

Changes: https://git.openjdk.java.net/panama-foreign/pull/449/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=449&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261498
  Stats: 8 lines in 1 file changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/449.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/449/head:pull/449

PR: https://git.openjdk.java.net/panama-foreign/pull/449