[foreign-jextract] RFR: 8244337: jextract generates struct static utils class for typedef names only if struct name is empty

[Athijegannathan Sundararajan]

* generating a separate class for typedef name always.
* also taking care of case insensitive name collisions.

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Commit messages:
 - 8244337: jextract generates struct static utils class for typedef names only if struct name is empty

Changes: https://git.openjdk.java.net/panama-foreign/pull/143/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/143/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8244337
  Stats: 55 lines in 3 files changed: 34 ins; 10 del; 11 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/143.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/143/head:pull/143

PR: https://git.openjdk.java.net/panama-foreign/pull/143