RFR: 8277489: Rewrite JAAS UnixLoginModule with FFM [v6]

[Weijun Wang]

> Rewrite the native calls with FFM.

Weijun Wang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - address comments from Maurizio; support AIX-specific `_posix_getpwuid_r`; recover unsigned int
 - Merge branch 'master' into 8277489
 - fail early on Windows, and more comments
 - use size_t
 - error handling
 - rewrite without jextract
 - no tabs
 - the fix

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28931/files
  - new: https://git.openjdk.org/jdk/pull/28931/files/578f1d2e..b54ca67c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28931&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28931&range=04-05

  Stats: 5209 lines in 1977 files changed: 1372 ins; 600 del; 3237 mod
  Patch: https://git.openjdk.org/jdk/pull/28931.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28931/head:pull/28931

PR: https://git.openjdk.org/jdk/pull/28931