Fix CGI::Application::Plugin::FormState session restoration regression

[fglock]

Summary

Investigate and fix the CGI::Application::Plugin::FormState regression in PerlOnJava.

Evidence

• Distribution: CGI-Application-Plugin-FormState v0.12
• Archived CPAN run: 20260824-215523-35400
• Regression: PASS → FAIL compared with the previous recorded run.
• PerlOnJava result: 86/113 tests passed; 27 subtests failed in 5 of 10 test programs.
• System Perl result: the same upstream suite passed 113/113 tests across all 10 test programs.

The failures are concentrated in session restoration. Tests in t/01-basic.t,
t/02-expires.t, t/03-storage_name.t, t/20-old-style-basic.t, and
t/21-old-style-expires.t expect a previously initialized session and stored
form values, but receive undef. Loading, deletion, auto-configuration, and
POD tests pass.

Investigation scope

1. Reproduce the failing tests with both PerlOnJava backends and capture the
   exact CGI/session dependency load order.
2. Compare session identifiers, cookies, serialization, and storage contents
   between the first and second simulated webapp requests.
3. Check for regressions in CGI::Session, CGI::Application::Plugin::Session,
   filesystem storage, child-process state, or PerlOnJava request lifecycle.
4. Reduce the cause to a focused PerlOnJava regression test, validated under
   system Perl first.
5. Restore the full unmodified upstream suite and verify both backends.