[foreign-jextract] RFR: 8248474: jextract uses header file name as part of identifier

[Athijegannathan Sundararajan]

Generating safe class name for header class

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Commit messages:
 - 8248474: jextract uses header file name as part of identifier

Changes: https://git.openjdk.java.net/panama-foreign/pull/218/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/218/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8248474
  Stats: 105 lines in 4 files changed: 100 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/218.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/218/head:pull/218

PR: https://git.openjdk.java.net/panama-foreign/pull/218