[foreign-jextract] [Rev 01] RFR: 8243978: jextract should generate separate classes with static util methods for each struct, union

[Athijegannathan Sundararajan]

> JavaSourceBuilder refactored. HeaderBuilder, StructBuilder are added.

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

  ConstantHelper classes are added from OutputFactory.

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/133/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/133/files/8284555a..2edc060b

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/133/webrev.01
 - incr: https://webrevs.openjdk.java.net/panama-foreign/133/webrev.00-01

  Stats: 26 lines in 4 files changed: 8 ins; 17 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/133.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/133/head:pull/133

PR: https://git.openjdk.java.net/panama-foreign/pull/133