[foreign-jextract] [Rev 01] RFR: 8244728: jextract generates separate nested class for struct and union typedefs

[Athijegannathan Sundararajan]

> * adding a subclass for struct/union typedefs rather than separate classes
> * piggybacking fix for MemoryLayout::offset->MemoryLayout::bitOffset change

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last
revision:

  added missing assertTrue calls.

-------------

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/159/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/159/files/7d8422dc..76000573

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/159/webrev.01
 - incr: https://webrevs.openjdk.java.net/panama-foreign/159/webrev.00-01

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/159.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/159/head:pull/159

PR: https://git.openjdk.java.net/panama-foreign/pull/159